Buffer

Buffer objects are used to represent a fixed-length sequence of bytes. Many Node.js APIs support Buffers.

The Buffer class is a subclass of JavaScript's <Uint8Array> class and extends it with methods that cover additional use cases. Node.js APIs accept plain <Uint8Array>s wherever Buffers are supported as well.

While the Buffer class is available within the global scope, it is still recommended to explicitly reference it via an import or require statement.

JavaScript modules

import { Buffer } from 'node:buffer';

// Creates a zero-filled Buffer of length 10.
const buf1 = Buffer.alloc(10);

// Creates a Buffer of length 10,
// filled with bytes which all have the value `1`.
const buf2 = Buffer.alloc(10, 1);

// Creates an uninitialized buffer of length 10.
// This is faster than calling Buffer.alloc() but the returned
// Buffer instance might contain old data that needs to be
// overwritten using fill(), write(), or other functions that fill the Buffer's
// contents.
const buf3 = Buffer.allocUnsafe(10);

// Creates a Buffer containing the bytes [1, 2, 3].
const buf4 = Buffer.from([1, 2, 3]);

// Creates a Buffer containing the bytes [1, 1, 1, 1] – the entries
// are all truncated using `(value & 255)` to fit into the range 0–255.
const buf5 = Buffer.from([257, 257.5, -255, '1']);

// Creates a Buffer containing the UTF-8-encoded bytes for the string 'tést':
// [0x74, 0xc3, 0xa9, 0x73, 0x74] (in hexadecimal notation)
// [116, 195, 169, 115, 116] (in decimal notation)
const buf6 = Buffer.from('tést');

// Creates a Buffer containing the Latin-1 bytes [0x74, 0xe9, 0x73, 0x74].
const buf7 = Buffer.from('tést', 'latin1');

CommonJS

const { Buffer } = require('node:buffer');

// Creates a zero-filled Buffer of length 10.
const buf1 = Buffer.alloc(10);

// Creates a Buffer of length 10,
// filled with bytes which all have the value `1`.
const buf2 = Buffer.alloc(10, 1);

// Creates an uninitialized buffer of length 10.
// This is faster than calling Buffer.alloc() but the returned
// Buffer instance might contain old data that needs to be
// overwritten using fill(), write(), or other functions that fill the Buffer's
// contents.
const buf3 = Buffer.allocUnsafe(10);

// Creates a Buffer containing the bytes [1, 2, 3].
const buf4 = Buffer.from([1, 2, 3]);

// Creates a Buffer containing the bytes [1, 1, 1, 1] – the entries
// are all truncated using `(value & 255)` to fit into the range 0–255.
const buf5 = Buffer.from([257, 257.5, -255, '1']);

// Creates a Buffer containing the UTF-8-encoded bytes for the string 'tést':
// [0x74, 0xc3, 0xa9, 0x73, 0x74] (in hexadecimal notation)
// [116, 195, 169, 115, 116] (in decimal notation)
const buf6 = Buffer.from('tést');

// Creates a Buffer containing the Latin-1 bytes [0x74, 0xe9, 0x73, 0x74].
const buf7 = Buffer.from('tést', 'latin1');

Buffers and character encodings

History

Version	Changes
v15.7.0, v14.18.0	Introduced `base64url` encoding.
v6.4.0	Introduced `latin1` as an alias for `binary`.
v5.0.0	Removed the deprecated `raw` and `raws` encodings.

When converting between Buffers and strings, a character encoding may be specified. If no character encoding is specified, UTF-8 will be used as the default.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from('hello world', 'utf8');

console.log(buf.toString('hex'));
// Prints: 68656c6c6f20776f726c64
console.log(buf.toString('base64'));
// Prints: aGVsbG8gd29ybGQ=

console.log(Buffer.from('fhqwhgads', 'utf8'));
// Prints: <Buffer 66 68 71 77 68 67 61 64 73>
console.log(Buffer.from('fhqwhgads', 'utf16le'));
// Prints: <Buffer 66 00 68 00 71 00 77 00 68 00 67 00 61 00 64 00 73 00>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from('hello world', 'utf8');

console.log(buf.toString('hex'));
// Prints: 68656c6c6f20776f726c64
console.log(buf.toString('base64'));
// Prints: aGVsbG8gd29ybGQ=

console.log(Buffer.from('fhqwhgads', 'utf8'));
// Prints: <Buffer 66 68 71 77 68 67 61 64 73>
console.log(Buffer.from('fhqwhgads', 'utf16le'));
// Prints: <Buffer 66 00 68 00 71 00 77 00 68 00 67 00 61 00 64 00 73 00>

Node.js buffers accept all case variations of encoding strings that they receive. For example, UTF-8 can be specified as 'utf8', 'UTF8', or 'uTf8'.

The character encodings currently supported by Node.js are the following:

'utf8' (alias: 'utf-8'): Multi-byte encoded Unicode characters. Many web pages and other document formats use UTF-8. This is the default character encoding. When decoding a Buffer into a string that does not exclusively contain valid UTF-8 data, the Unicode replacement character U+FFFD � will be used to represent those errors.
'utf16le' (alias: 'utf-16le'): Multi-byte encoded Unicode characters. Unlike 'utf8', each character in the string will be encoded using either 2 or 4 bytes. Node.js only supports the little-endian variant of UTF-16.
'latin1': Latin-1 stands for ISO-8859-1. This character encoding only supports the Unicode characters from U+0000 to U+00FF. Each character is encoded using a single byte. Characters that do not fit into that range are truncated and will be mapped to characters in that range.

Converting a Buffer into a string using one of the above is referred to as decoding, and converting a string into a Buffer is referred to as encoding.

Node.js also supports the following binary-to-text encodings. For binary-to-text encodings, the naming convention is reversed: Converting a Buffer into a string is typically referred to as encoding, and converting a string into a Buffer as decoding.

'base64': Base64 encoding. When creating a Buffer from a string, this encoding will also correctly accept "URL and Filename Safe Alphabet" as specified in RFC 4648, Section 5. Whitespace characters such as spaces, tabs, and new lines contained within the base64-encoded string are ignored.
'base64url': base64url encoding as specified in RFC 4648, Section 5. When creating a Buffer from a string, this encoding will also correctly accept regular base64-encoded strings. When encoding a Buffer to a string, this encoding will omit padding.
'hex': Encode each byte as two hexadecimal characters. Data truncation may occur when decoding strings that do not exclusively consist of an even number of hexadecimal characters. See below for an example.

The following legacy character encodings are also supported:

'ascii': For 7-bit ASCII data only. When encoding a string into a Buffer, this is equivalent to using 'latin1'. When decoding a Buffer into a string, using this encoding will additionally unset the highest bit of each byte before decoding as 'latin1'. Generally, there should be no reason to use this encoding, as 'utf8' (or, if the data is known to always be ASCII-only, 'latin1') will be a better choice when encoding or decoding ASCII-only text. It is only provided for legacy compatibility.
'binary': Alias for 'latin1'. The name of this encoding can be very misleading, as all of the encodings listed here convert between strings and binary data. For converting between strings and Buffers, typically 'utf8' is the right choice.
'ucs2', 'ucs-2': Aliases of 'utf16le'. UCS-2 used to refer to a variant of UTF-16 that did not support characters that had code points larger than U+FFFF. In Node.js, these code points are always supported.

JavaScript modules

import { Buffer } from 'node:buffer';

Buffer.from('1ag123', 'hex');
// Prints <Buffer 1a>, data truncated when first non-hexadecimal value
// ('g') encountered.

Buffer.from('1a7', 'hex');
// Prints <Buffer 1a>, data truncated when data ends in single digit ('7').

Buffer.from('1634', 'hex');
// Prints <Buffer 16 34>, all data represented.

CommonJS

const { Buffer } = require('node:buffer');

Buffer.from('1ag123', 'hex');
// Prints <Buffer 1a>, data truncated when first non-hexadecimal value
// ('g') encountered.

Buffer.from('1a7', 'hex');
// Prints <Buffer 1a>, data truncated when data ends in single digit ('7').

Buffer.from('1634', 'hex');
// Prints <Buffer 16 34>, all data represented.

Modern Web browsers follow the WHATWG Encoding Standard which aliases both 'latin1' and 'ISO-8859-1' to 'win-1252'. This means that while doing something like http.get(), if the returned charset is one of those listed in the WHATWG specification it is possible that the server actually returned 'win-1252'-encoded data, and using 'latin1' encoding may incorrectly decode the characters.

Buffers and TypedArrays

History

Version	Changes
v3.0.0	The `Buffer` class now inherits from `Uint8Array`.

Buffer instances are also JavaScript <Uint8Array> and <TypedArray> instances. All <TypedArray> methods and properties are available on Buffers. There are, however, subtle incompatibilities between the Buffer API and the <TypedArray> API.

In particular:

While TypedArray.prototype.slice() creates a copy of part of the TypedArray, Buffer.prototype.slice() creates a view over the existing Buffer without copying. This behavior can be surprising, and only exists for legacy compatibility. TypedArray.prototype.subarray() can be used to achieve the behavior of Buffer.prototype.slice() on both Buffers and other TypedArrays and should be preferred.
buf.toString() is incompatible with its TypedArray equivalent.
A number of methods, e.g. buf.indexOf(), support additional arguments.

There are two ways to create new <TypedArray> instances from a Buffer:

Passing a Buffer to a <TypedArray> constructor will copy the Buffer's contents, interpreted as an array of integers, and not as a byte sequence of the target type.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([1, 2, 3, 4]);
const uint32array = new Uint32Array(buf);

console.log(uint32array);

// Prints: Uint32Array(4) [ 1, 2, 3, 4 ]

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([1, 2, 3, 4]);
const uint32array = new Uint32Array(buf);

console.log(uint32array);

// Prints: Uint32Array(4) [ 1, 2, 3, 4 ]

Passing the Buffer's underlying <ArrayBuffer> will create a <TypedArray> that shares its memory with the Buffer.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from('hello', 'utf16le');
const uint16array = new Uint16Array(
  buf.buffer,
  buf.byteOffset,
  buf.length / Uint16Array.BYTES_PER_ELEMENT);

console.log(uint16array);

// Prints: Uint16Array(5) [ 104, 101, 108, 108, 111 ]

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from('hello', 'utf16le');
const uint16array = new Uint16Array(
  buf.buffer,
  buf.byteOffset,
  buf.length / Uint16Array.BYTES_PER_ELEMENT);

console.log(uint16array);

// Prints: Uint16Array(5) [ 104, 101, 108, 108, 111 ]

It is possible to create a new Buffer that shares the same allocated memory as a <TypedArray> instance by using the TypedArray object's .buffer property in the same way. Buffer.from() behaves like new Uint8Array() in this context.

JavaScript modules

import { Buffer } from 'node:buffer';

const arr = new Uint16Array(2);

arr[0] = 5000;
arr[1] = 4000;

// Copies the contents of `arr`.
const buf1 = Buffer.from(arr);

// Shares memory with `arr`.
const buf2 = Buffer.from(arr.buffer);

console.log(buf1);
// Prints: <Buffer 88 a0>
console.log(buf2);
// Prints: <Buffer 88 13 a0 0f>

arr[1] = 6000;

console.log(buf1);
// Prints: <Buffer 88 a0>
console.log(buf2);
// Prints: <Buffer 88 13 70 17>

CommonJS

const { Buffer } = require('node:buffer');

const arr = new Uint16Array(2);

arr[0] = 5000;
arr[1] = 4000;

// Copies the contents of `arr`.
const buf1 = Buffer.from(arr);

// Shares memory with `arr`.
const buf2 = Buffer.from(arr.buffer);

console.log(buf1);
// Prints: <Buffer 88 a0>
console.log(buf2);
// Prints: <Buffer 88 13 a0 0f>

arr[1] = 6000;

console.log(buf1);
// Prints: <Buffer 88 a0>
console.log(buf2);
// Prints: <Buffer 88 13 70 17>

When creating a Buffer using a <TypedArray>'s .buffer, it is possible to use only a portion of the underlying <ArrayBuffer> by passing in byteOffset and length parameters.

JavaScript modules

import { Buffer } from 'node:buffer';

const arr = new Uint16Array(20);
const buf = Buffer.from(arr.buffer, 0, 16);

console.log(buf.length);
// Prints: 16

CommonJS

const { Buffer } = require('node:buffer');

const arr = new Uint16Array(20);
const buf = Buffer.from(arr.buffer, 0, 16);

console.log(buf.length);
// Prints: 16

The Buffer.from() and TypedArray.from() have different signatures and implementations. Specifically, the <TypedArray> variants accept a second argument that is a mapping function that is invoked on every element of the typed array:

TypedArray.from(source[, mapFn[, thisArg]])

The Buffer.from() method, however, does not support the use of a mapping function:

Buffer.from(array)
Buffer.from(buffer)
Buffer.from(arrayBuffer[, byteOffset[, length]])
Buffer.from(string[, encoding])

Buffer methods are callable with `Uint8Array` instances

All methods on the Buffer prototype are callable with a Uint8Array instance.

const { toString, write } = Buffer.prototype;

const uint8array = new Uint8Array(5);

write.call(uint8array, 'hello', 0, 5, 'utf8'); // 5
// <Uint8Array 68 65 6c 6c 6f>

toString.call(uint8array, 'utf8'); // 'hello'
jscopy

Buffers and iteration

Buffer instances can be iterated over using for..of syntax:

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([1, 2, 3]);

for (const b of buf) {
  console.log(b);
}
// Prints:
//   1
//   2
//   3

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([1, 2, 3]);

for (const b of buf) {
  console.log(b);
}
// Prints:
//   1
//   2
//   3

Additionally, the buf.values(), buf.keys(), and buf.entries() methods can be used to create iterators.

Class: `Blob`

Added in: v15.7.0, v14.18.0

History

Version	Changes
v18.0.0, v16.17.0	No longer experimental.

A <Blob> encapsulates immutable, raw data that can be safely shared across multiple worker threads.

`new buffer.Blob([sources[, options]])`

Added in: v15.7.0, v14.18.0

History

Version	Changes
v16.7.0	Added the standard `endings` option to replace line-endings, and removed the non-standard `encoding` option.

sources <string[]> | <ArrayBuffer[]> | <TypedArray[]> | <DataView[]> | <Blob[]> An array of string, <ArrayBuffer>, <TypedArray>, <DataView>, or <Blob> objects, or any mix of such objects, that will be stored within the Blob.
options <Object>
- endings <string> One of either 'transparent' or 'native'. When set to 'native', line endings in string source parts will be converted to the platform native line-ending as specified by require('node:os').EOL.
- type <string> The Blob content-type. The intent is for type to convey the MIME media type of the data, however no validation of the type format is performed.

Creates a new Blob object containing a concatenation of the given sources.

<ArrayBuffer>, <TypedArray>, <DataView>, and <Buffer> sources are copied into the 'Blob' and can therefore be safely modified after the 'Blob' is created.

String sources are encoded as UTF-8 byte sequences and copied into the Blob. Unmatched surrogate pairs within each string part will be replaced by Unicode U+FFFD replacement characters.

`blob.arrayBuffer()`

Added in: v15.7.0, v14.18.0

Returns: <Promise>

Returns a promise that fulfills with an <ArrayBuffer> containing a copy of the Blob data.

`blob.bytes()`

Added in: v22.3.0, v20.16.0

The blob.bytes() method returns the byte of the Blob object as a Promise<Uint8Array>.

const blob = new Blob(['hello']);
blob.bytes().then((bytes) => {
  console.log(bytes); // Outputs: Uint8Array(5) [ 104, 101, 108, 108, 111 ]
});
jscopy

`blob.size`

Added in: v15.7.0, v14.18.0

The total size of the Blob in bytes.

`blob.slice([start[, end[, type]]])`

Added in: v15.7.0, v14.18.0

start <number> The starting index.
end <number> The ending index.
type <string> The content-type for the new Blob

Creates and returns a new Blob containing a subset of this Blob objects data. The original Blob is not altered.

`blob.stream()`

Added in: v16.7.0

Returns: <ReadableStream>

Returns a new ReadableStream that allows the content of the Blob to be read.

`blob.text()`

Added in: v15.7.0, v14.18.0

Returns: <Promise>

Returns a promise that fulfills with the contents of the Blob decoded as a UTF-8 string.

`blob.type`

Added in: v15.7.0, v14.18.0

Type: <string>

The content-type of the Blob.

`Blob` objects and `MessageChannel`

Once a <Blob> object is created, it can be sent via MessagePort to multiple destinations without transferring or immediately copying the data. The data contained by the Blob is copied only when the arrayBuffer() or text() methods are called.

JavaScript modules

import { Blob } from 'node:buffer';
import { setTimeout as delay } from 'node:timers/promises';

const blob = new Blob(['hello there']);

const mc1 = new MessageChannel();
const mc2 = new MessageChannel();

mc1.port1.onmessage = async ({ data }) => {
  console.log(await data.arrayBuffer());
  mc1.port1.close();
};

mc2.port1.onmessage = async ({ data }) => {
  await delay(1000);
  console.log(await data.arrayBuffer());
  mc2.port1.close();
};

mc1.port2.postMessage(blob);
mc2.port2.postMessage(blob);

// The Blob is still usable after posting.
blob.text().then(console.log);

CommonJS

const { Blob } = require('node:buffer');
const { setTimeout: delay } = require('node:timers/promises');

const blob = new Blob(['hello there']);

const mc1 = new MessageChannel();
const mc2 = new MessageChannel();

mc1.port1.onmessage = async ({ data }) => {
  console.log(await data.arrayBuffer());
  mc1.port1.close();
};

mc2.port1.onmessage = async ({ data }) => {
  await delay(1000);
  console.log(await data.arrayBuffer());
  mc2.port1.close();
};

mc1.port2.postMessage(blob);
mc2.port2.postMessage(blob);

// The Blob is still usable after posting.
blob.text().then(console.log);

Class: `Buffer`

The Buffer class is a global type for dealing with binary data directly. It can be constructed in a variety of ways.

Static method: `Buffer.alloc(size[, fill[, encoding]])`

Added in: v5.10.0

History

Version	Changes
v20.0.0	Throw ERR_INVALID_ARG_TYPE or ERR_OUT_OF_RANGE instead of ERR_INVALID_ARG_VALUE for invalid input arguments.
v15.0.0	Throw ERR_INVALID_ARG_VALUE instead of ERR_INVALID_OPT_VALUE for invalid input arguments.
v10.0.0	Attempting to fill a non-zero length buffer with a zero length buffer triggers a thrown exception.
v10.0.0	Specifying an invalid string for `fill` triggers a thrown exception.
v8.9.3	Specifying an invalid string for `fill` now results in a zero-filled buffer.

size <integer> The desired length of the new Buffer.
fill <string> | <Buffer> | <Uint8Array> | <integer> A value to pre-fill the new Buffer with. Default: 0.
encoding <string> If fill is a string, this is its encoding. Default: 'utf8'.
Returns: <Buffer>

Allocates a new Buffer of size bytes. If fill is undefined, the Buffer will be zero-filled.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.alloc(5);

console.log(buf);
// Prints: <Buffer 00 00 00 00 00>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.alloc(5);

console.log(buf);
// Prints: <Buffer 00 00 00 00 00>

If size is larger than buffer.constants.MAX_LENGTH or smaller than 0, ERR_OUT_OF_RANGE is thrown.

If fill is specified, the allocated Buffer will be initialized by calling buf.fill(fill).

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.alloc(5, 'a');

console.log(buf);
// Prints: <Buffer 61 61 61 61 61>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.alloc(5, 'a');

console.log(buf);
// Prints: <Buffer 61 61 61 61 61>

If both fill and encoding are specified, the allocated Buffer will be initialized by calling buf.fill(fill, encoding).

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'base64');

console.log(buf);
// Prints: <Buffer 68 65 6c 6c 6f 20 77 6f 72 6c 64>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'base64');

console.log(buf);
// Prints: <Buffer 68 65 6c 6c 6f 20 77 6f 72 6c 64>

Calling Buffer.alloc() can be measurably slower than the alternative Buffer.allocUnsafe() but ensures that the newly created Buffer instance contents will never contain sensitive data from previous allocations, including data that might not have been allocated for Buffers.

A TypeError will be thrown if size is not a number.

Static method: `Buffer.allocUnsafe(size)`

Added in: v5.10.0

History

Version	Changes
v20.0.0	Throw ERR_INVALID_ARG_TYPE or ERR_OUT_OF_RANGE instead of ERR_INVALID_ARG_VALUE for invalid input arguments.
v15.0.0	Throw ERR_INVALID_ARG_VALUE instead of ERR_INVALID_OPT_VALUE for invalid input arguments.
v7.0.0	Passing a negative `size` will now throw an error.

size <integer> The desired length of the new Buffer.
Returns: <Buffer>

Allocates a new Buffer of size bytes. If size is larger than buffer.constants.MAX_LENGTH or smaller than 0, ERR_OUT_OF_RANGE is thrown.

The underlying memory for Buffer instances created in this way is not initialized. The contents of the newly created Buffer are unknown and may contain sensitive data. Use Buffer.alloc() instead to initialize Buffer instances with zeroes.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(10);

console.log(buf);
// Prints (contents may vary): <Buffer a0 8b 28 3f 01 00 00 00 50 32>

buf.fill(0);

console.log(buf);
// Prints: <Buffer 00 00 00 00 00 00 00 00 00 00>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(10);

console.log(buf);
// Prints (contents may vary): <Buffer a0 8b 28 3f 01 00 00 00 50 32>

buf.fill(0);

console.log(buf);
// Prints: <Buffer 00 00 00 00 00 00 00 00 00 00>

A TypeError will be thrown if size is not a number.

The Buffer module pre-allocates an internal Buffer instance of size Buffer.poolSize that is used as a pool for the fast allocation of new Buffer instances created using Buffer.allocUnsafe(), Buffer.from(array), Buffer.from(string), and Buffer.concat() only when size is less than Buffer.poolSize >>> 1 (floor of Buffer.poolSize divided by two).

Use of this pre-allocated internal memory pool is a key difference between calling Buffer.alloc(size, fill) vs. Buffer.allocUnsafe(size).fill(fill). Specifically, Buffer.alloc(size, fill) will never use the internal Buffer pool, while Buffer.allocUnsafe(size).fill(fill) will use the internal Buffer pool if size is less than or equal to half Buffer.poolSize. The difference is subtle but can be important when an application requires the additional performance that Buffer.allocUnsafe() provides.

Static method: `Buffer.allocUnsafeSlow(size)`

Added in: v5.12.0

History

Version	Changes
v20.0.0	Throw ERR_INVALID_ARG_TYPE or ERR_OUT_OF_RANGE instead of ERR_INVALID_ARG_VALUE for invalid input arguments.
v15.0.0	Throw ERR_INVALID_ARG_VALUE instead of ERR_INVALID_OPT_VALUE for invalid input arguments.

size <integer> The desired length of the new Buffer.
Returns: <Buffer>

Allocates a new Buffer of size bytes. If size is larger than buffer.constants.MAX_LENGTH or smaller than 0, ERR_OUT_OF_RANGE is thrown. A zero-length Buffer is created if size is 0.

The underlying memory for Buffer instances created in this way is not initialized. The contents of the newly created Buffer are unknown and may contain sensitive data. Use buf.fill(0) to initialize such Buffer instances with zeroes.

When using Buffer.allocUnsafe() to allocate new Buffer instances, allocations less than Buffer.poolSize >>> 1 (32KiB when default poolSize is used) are sliced from a single pre-allocated Buffer. This allows applications to avoid the garbage collection overhead of creating many individually allocated Buffer instances. This approach improves both performance and memory usage by eliminating the need to track and clean up as many individual ArrayBuffer objects.

However, in the case where a developer may need to retain a small chunk of memory from a pool for an indeterminate amount of time, it may be appropriate to create an un-pooled Buffer instance using Buffer.allocUnsafeSlow() and then copying out the relevant bits.

JavaScript modules

import { Buffer } from 'node:buffer';

// Need to keep around a few small chunks of memory.
const store = [];

socket.on('readable', () => {
  let data;
  while (null !== (data = readable.read())) {
    // Allocate for retained data.
    const sb = Buffer.allocUnsafeSlow(10);

    // Copy the data into the new allocation.
    data.copy(sb, 0, 0, 10);

    store.push(sb);
  }
});

CommonJS

const { Buffer } = require('node:buffer');

// Need to keep around a few small chunks of memory.
const store = [];

socket.on('readable', () => {
  let data;
  while (null !== (data = readable.read())) {
    // Allocate for retained data.
    const sb = Buffer.allocUnsafeSlow(10);

    // Copy the data into the new allocation.
    data.copy(sb, 0, 0, 10);

    store.push(sb);
  }
});

A TypeError will be thrown if size is not a number.

Static method: `Buffer.byteLength(string[, encoding])`

Added in: v0.1.90

History

Version	Changes
v7.0.0	Passing invalid input will now throw an error.
v5.10.0	The `string` parameter can now be any `TypedArray`, `DataView` or `ArrayBuffer`.

string <string> | <Buffer> | <TypedArray> | <DataView> | <ArrayBuffer> | <SharedArrayBuffer> A value to calculate the length of.
encoding <string> If string is a string, this is its encoding. Default: 'utf8'.
Returns: <integer> The number of bytes contained within string.

Returns the byte length of a string when encoded using encoding. This is not the same as String.prototype.length, which does not account for the encoding that is used to convert the string into bytes.

For 'base64', 'base64url', and 'hex', this function assumes valid input. For strings that contain non-base64/hex-encoded data (e.g. whitespace), the return value might be greater than the length of a Buffer created from the string.

JavaScript modules

import { Buffer } from 'node:buffer';

const str = '\u00bd + \u00bc = \u00be';

console.log(`${str}: ${str.length} characters, ` +
            `${Buffer.byteLength(str, 'utf8')} bytes`);
// Prints: ½ + ¼ = ¾: 9 characters, 12 bytes

CommonJS

const { Buffer } = require('node:buffer');

const str = '\u00bd + \u00bc = \u00be';

console.log(`${str}: ${str.length} characters, ` +
            `${Buffer.byteLength(str, 'utf8')} bytes`);
// Prints: ½ + ¼ = ¾: 9 characters, 12 bytes

When string is a <Buffer> | <DataView> | <TypedArray> | <ArrayBuffer> | <SharedArrayBuffer>, the byte length as reported by .byteLength is returned.

Static method: `Buffer.compare(buf1, buf2)`

Added in: v0.11.13

History

Version	Changes
v8.0.0	The arguments can now be `Uint8Array`s.

buf1 <Buffer> | <Uint8Array>
buf2 <Buffer> | <Uint8Array>
Returns: <integer> Either -1, 0, or 1, depending on the result of the comparison. See buf.compare() for details.

Compares buf1 to buf2, typically for the purpose of sorting arrays of Buffer instances. This is equivalent to calling buf1.compare(buf2).

JavaScript modules

import { Buffer } from 'node:buffer';

const buf1 = Buffer.from('1234');
const buf2 = Buffer.from('0123');
const arr = [buf1, buf2];

console.log(arr.sort(Buffer.compare));
// Prints: [ <Buffer 30 31 32 33>, <Buffer 31 32 33 34> ]
// (This result is equal to: [buf2, buf1].)

CommonJS

const { Buffer } = require('node:buffer');

const buf1 = Buffer.from('1234');
const buf2 = Buffer.from('0123');
const arr = [buf1, buf2];

console.log(arr.sort(Buffer.compare));
// Prints: [ <Buffer 30 31 32 33>, <Buffer 31 32 33 34> ]
// (This result is equal to: [buf2, buf1].)

Static method: `Buffer.concat(list[, totalLength])`

Added in: v0.7.11

History

Version	Changes
v8.0.0	The elements of `list` can now be `Uint8Array`s.

list <Buffer[]> | <Uint8Array[]> List of Buffer or <Uint8Array> instances to concatenate.
totalLength <integer> Total length of the Buffer instances in list when concatenated.
Returns: <Buffer>

Returns a new Buffer which is the result of concatenating all the Buffer instances in the list together.

If the list has no items, or if the totalLength is 0, then a new zero-length Buffer is returned.

If totalLength is not provided, it is calculated from the Buffer instances in list by adding their lengths.

If totalLength is provided, it must be an unsigned integer. If the combined length of the Buffers in list exceeds totalLength, the result is truncated to totalLength. If the combined length of the Buffers in list is less than totalLength, the remaining space is filled with zeros.

JavaScript modules

import { Buffer } from 'node:buffer';

// Create a single `Buffer` from a list of three `Buffer` instances.

const buf1 = Buffer.alloc(10);
const buf2 = Buffer.alloc(14);
const buf3 = Buffer.alloc(18);
const totalLength = buf1.length + buf2.length + buf3.length;

console.log(totalLength);
// Prints: 42

const bufA = Buffer.concat([buf1, buf2, buf3], totalLength);

console.log(bufA);
// Prints: <Buffer 00 00 00 00 ...>
console.log(bufA.length);
// Prints: 42

CommonJS

const { Buffer } = require('node:buffer');

// Create a single `Buffer` from a list of three `Buffer` instances.

const buf1 = Buffer.alloc(10);
const buf2 = Buffer.alloc(14);
const buf3 = Buffer.alloc(18);
const totalLength = buf1.length + buf2.length + buf3.length;

console.log(totalLength);
// Prints: 42

const bufA = Buffer.concat([buf1, buf2, buf3], totalLength);

console.log(bufA);
// Prints: <Buffer 00 00 00 00 ...>
console.log(bufA.length);
// Prints: 42

Buffer.concat() may also use the internal Buffer pool like Buffer.allocUnsafe() does.

Static method: `Buffer.copyBytesFrom(view[, offset[, length]])`

Added in: v19.8.0, v18.16.0

view <TypedArray> The <TypedArray> to copy.
offset <integer> The starting offset within view. Default: 0.
length <integer> The number of elements from view to copy. Default: view.length - offset.
Returns: <Buffer>

Copies the underlying memory of view into a new Buffer.

const u16 = new Uint16Array([0, 0xffff]);
const buf = Buffer.copyBytesFrom(u16, 1, 1);
u16[1] = 0;
console.log(buf.length); // 2
console.log(buf[0]); // 255
console.log(buf[1]); // 255
jscopy

Static method: `Buffer.from(array)`

Added in: v5.10.0

array <integer[]>
Returns: <Buffer>

Allocates a new Buffer using an array of bytes in the range 0 – 255. Array entries outside that range will be truncated to fit into it.

JavaScript modules

import { Buffer } from 'node:buffer';

// Creates a new Buffer containing the UTF-8 bytes of the string 'buffer'.
const buf = Buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);

CommonJS

const { Buffer } = require('node:buffer');

// Creates a new Buffer containing the UTF-8 bytes of the string 'buffer'.
const buf = Buffer.from([0x62, 0x75, 0x66, 0x66, 0x65, 0x72]);

If array is an Array-like object (that is, one with a length property of type number), it is treated as if it is an array, unless it is a Buffer or a Uint8Array. This means all other TypedArray variants get treated as an Array. To create a Buffer from the bytes backing a TypedArray, use Buffer.copyBytesFrom().

A TypeError will be thrown if array is not an Array or another type appropriate for Buffer.from() variants.

Buffer.from(array) and Buffer.from(string) may also use the internal Buffer pool like Buffer.allocUnsafe() does.

Static method: `Buffer.from(arrayBuffer[, byteOffset[, length]])`

Added in: v5.10.0

arrayBuffer <ArrayBuffer> | <SharedArrayBuffer> An <ArrayBuffer>, <SharedArrayBuffer>, for example the .buffer property of a <TypedArray>.
byteOffset <integer> Index of first byte to expose. Default: 0.
length <integer> Number of bytes to expose. Default: arrayBuffer.byteLength - byteOffset.
Returns: <Buffer>

This creates a view of the <ArrayBuffer> without copying the underlying memory. For example, when passed a reference to the .buffer property of a <TypedArray> instance, the newly created Buffer will share the same allocated memory as the <TypedArray>'s underlying ArrayBuffer.

JavaScript modules

import { Buffer } from 'node:buffer';

const arr = new Uint16Array(2);

arr[0] = 5000;
arr[1] = 4000;

// Shares memory with `arr`.
const buf = Buffer.from(arr.buffer);

console.log(buf);
// Prints: <Buffer 88 13 a0 0f>

// Changing the original Uint16Array changes the Buffer also.
arr[1] = 6000;

console.log(buf);
// Prints: <Buffer 88 13 70 17>

CommonJS

const { Buffer } = require('node:buffer');

const arr = new Uint16Array(2);

arr[0] = 5000;
arr[1] = 4000;

// Shares memory with `arr`.
const buf = Buffer.from(arr.buffer);

console.log(buf);
// Prints: <Buffer 88 13 a0 0f>

// Changing the original Uint16Array changes the Buffer also.
arr[1] = 6000;

console.log(buf);
// Prints: <Buffer 88 13 70 17>

The optional byteOffset and length arguments specify a memory range within the arrayBuffer that will be shared by the Buffer.

JavaScript modules

import { Buffer } from 'node:buffer';

const ab = new ArrayBuffer(10);
const buf = Buffer.from(ab, 0, 2);

console.log(buf.length);
// Prints: 2

CommonJS

const { Buffer } = require('node:buffer');

const ab = new ArrayBuffer(10);
const buf = Buffer.from(ab, 0, 2);

console.log(buf.length);
// Prints: 2

A TypeError will be thrown if arrayBuffer is not an <ArrayBuffer> or a <SharedArrayBuffer> or another type appropriate for Buffer.from() variants.

It is important to remember that a backing ArrayBuffer can cover a range of memory that extends beyond the bounds of a TypedArray view. A new Buffer created using the buffer property of a TypedArray may extend beyond the range of the TypedArray:

JavaScript modules

import { Buffer } from 'node:buffer';

const arrA = Uint8Array.from([0x63, 0x64, 0x65, 0x66]); // 4 elements
const arrB = new Uint8Array(arrA.buffer, 1, 2); // 2 elements
console.log(arrA.buffer === arrB.buffer); // true

const buf = Buffer.from(arrB.buffer);
console.log(buf);
// Prints: <Buffer 63 64 65 66>

CommonJS

const { Buffer } = require('node:buffer');

const arrA = Uint8Array.from([0x63, 0x64, 0x65, 0x66]); // 4 elements
const arrB = new Uint8Array(arrA.buffer, 1, 2); // 2 elements
console.log(arrA.buffer === arrB.buffer); // true

const buf = Buffer.from(arrB.buffer);
console.log(buf);
// Prints: <Buffer 63 64 65 66>

Static method: `Buffer.from(buffer)`

Added in: v5.10.0

buffer <Buffer> | <Uint8Array> An existing Buffer or <Uint8Array> from which to copy data.
Returns: <Buffer>

Copies the passed buffer data onto a new Buffer instance.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf1 = Buffer.from('buffer');
const buf2 = Buffer.from(buf1);

buf1[0] = 0x61;

console.log(buf1.toString());
// Prints: auffer
console.log(buf2.toString());
// Prints: buffer

CommonJS

const { Buffer } = require('node:buffer');

const buf1 = Buffer.from('buffer');
const buf2 = Buffer.from(buf1);

buf1[0] = 0x61;

console.log(buf1.toString());
// Prints: auffer
console.log(buf2.toString());
// Prints: buffer

A TypeError will be thrown if buffer is not a Buffer or another type appropriate for Buffer.from() variants.

Static method: `Buffer.from(object[, offsetOrEncoding[, length]])`

Added in: v8.2.0

object <Object> An object supporting Symbol.toPrimitive or valueOf().
offsetOrEncoding <integer> | <string> A byte-offset or encoding.
length <integer> A length.
Returns: <Buffer>

For objects whose valueOf() function returns a value not strictly equal to object, returns Buffer.from(object.valueOf(), offsetOrEncoding, length).

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from(new String('this is a test'));
// Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from(new String('this is a test'));
// Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74>

For objects that support Symbol.toPrimitive, returns Buffer.from(object[Symbol.toPrimitive]('string'), offsetOrEncoding).

JavaScript modules

import { Buffer } from 'node:buffer';

class Foo {
  [Symbol.toPrimitive]() {
    return 'this is a test';
  }
}

const buf = Buffer.from(new Foo(), 'utf8');
// Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74>

CommonJS

const { Buffer } = require('node:buffer');

class Foo {
  [Symbol.toPrimitive]() {
    return 'this is a test';
  }
}

const buf = Buffer.from(new Foo(), 'utf8');
// Prints: <Buffer 74 68 69 73 20 69 73 20 61 20 74 65 73 74>

A TypeError will be thrown if object does not have the mentioned methods or is not of another type appropriate for Buffer.from() variants.

Static method: `Buffer.from(string[, encoding])`

Added in: v5.10.0

string <string> A string to encode.
encoding <string> The encoding of string. Default: 'utf8'.
Returns: <Buffer>

Creates a new Buffer containing string. The encoding parameter identifies the character encoding to be used when converting string into bytes.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf1 = Buffer.from('this is a tést');
const buf2 = Buffer.from('7468697320697320612074c3a97374', 'hex');

console.log(buf1.toString());
// Prints: this is a tést
console.log(buf2.toString());
// Prints: this is a tést
console.log(buf1.toString('latin1'));
// Prints: this is a tÃ©st

CommonJS

const { Buffer } = require('node:buffer');

const buf1 = Buffer.from('this is a tést');
const buf2 = Buffer.from('7468697320697320612074c3a97374', 'hex');

console.log(buf1.toString());
// Prints: this is a tést
console.log(buf2.toString());
// Prints: this is a tést
console.log(buf1.toString('latin1'));
// Prints: this is a tÃ©st

A TypeError will be thrown if string is not a string or another type appropriate for Buffer.from() variants.

Buffer.from(string) may also use the internal Buffer pool like Buffer.allocUnsafe() does.

Static method: `Buffer.isBuffer(obj)`

Added in: v0.1.101

obj <Object>
Returns: <boolean>

Returns true if obj is a Buffer, false otherwise.

JavaScript modules

import { Buffer } from 'node:buffer';

Buffer.isBuffer(Buffer.alloc(10)); // true
Buffer.isBuffer(Buffer.from('foo')); // true
Buffer.isBuffer('a string'); // false
Buffer.isBuffer([]); // false
Buffer.isBuffer(new Uint8Array(1024)); // false

CommonJS

const { Buffer } = require('node:buffer');

Buffer.isBuffer(Buffer.alloc(10)); // true
Buffer.isBuffer(Buffer.from('foo')); // true
Buffer.isBuffer('a string'); // false
Buffer.isBuffer([]); // false
Buffer.isBuffer(new Uint8Array(1024)); // false

Static method: `Buffer.isEncoding(encoding)`

Added in: v0.9.1

encoding <string> A character encoding name to check.
Returns: <boolean>

Returns true if encoding is the name of a supported character encoding, or false otherwise.

JavaScript modules

import { Buffer } from 'node:buffer';

console.log(Buffer.isEncoding('utf8'));
// Prints: true

console.log(Buffer.isEncoding('hex'));
// Prints: true

console.log(Buffer.isEncoding('utf/8'));
// Prints: false

console.log(Buffer.isEncoding(''));
// Prints: false

CommonJS

const { Buffer } = require('node:buffer');

console.log(Buffer.isEncoding('utf8'));
// Prints: true

console.log(Buffer.isEncoding('hex'));
// Prints: true

console.log(Buffer.isEncoding('utf/8'));
// Prints: false

console.log(Buffer.isEncoding(''));
// Prints: false

`Buffer.poolSize`

Added in: v0.11.3

History

Version	Changes
v26.3.0	Default raised from 8192 to 65536.

Type: <integer> Default: 65536

This is the size (in bytes) of pre-allocated internal Buffer instances used for pooling. This value may be modified.

`buf[index]`

index <integer>

The index operator [index] can be used to get and set the octet at position index in buf. The values refer to individual bytes, so the legal value range is between 0x00 and 0xFF (hex) or 0 and 255 (decimal).

This operator is inherited from Uint8Array, so its behavior on out-of-bounds access is the same as Uint8Array. In other words, buf[index] returns undefined when index is negative or greater or equal to buf.length, and buf[index] = value does not modify the buffer if index is negative or >= buf.length.

JavaScript modules

import { Buffer } from 'node:buffer';

// Copy an ASCII string into a `Buffer` one byte at a time.
// (This only works for ASCII-only strings. In general, one should use
// `Buffer.from()` to perform this conversion.)

const str = 'Node.js';
const buf = Buffer.allocUnsafe(str.length);

for (let i = 0; i < str.length; i++) {
  buf[i] = str.charCodeAt(i);
}

console.log(buf.toString('utf8'));
// Prints: Node.js

CommonJS

const { Buffer } = require('node:buffer');

// Copy an ASCII string into a `Buffer` one byte at a time.
// (This only works for ASCII-only strings. In general, one should use
// `Buffer.from()` to perform this conversion.)

const str = 'Node.js';
const buf = Buffer.allocUnsafe(str.length);

for (let i = 0; i < str.length; i++) {
  buf[i] = str.charCodeAt(i);
}

console.log(buf.toString('utf8'));
// Prints: Node.js

`buf.buffer`

Type: <ArrayBuffer> The underlying ArrayBuffer object based on which this Buffer object is created.

This ArrayBuffer is not guaranteed to correspond exactly to the original Buffer. See the notes on buf.byteOffset for details.

JavaScript modules

import { Buffer } from 'node:buffer';

const arrayBuffer = new ArrayBuffer(16);
const buffer = Buffer.from(arrayBuffer);

console.log(buffer.buffer === arrayBuffer);
// Prints: true

CommonJS

const { Buffer } = require('node:buffer');

const arrayBuffer = new ArrayBuffer(16);
const buffer = Buffer.from(arrayBuffer);

console.log(buffer.buffer === arrayBuffer);
// Prints: true

`buf.byteOffset`

Type: <integer> The byteOffset of the Buffer's underlying ArrayBuffer object.

When setting byteOffset in Buffer.from(ArrayBuffer, byteOffset, length), or sometimes when allocating a Buffer smaller than Buffer.poolSize, the buffer does not start from a zero offset on the underlying ArrayBuffer.

This can cause problems when accessing the underlying ArrayBuffer directly using buf.buffer, as other parts of the ArrayBuffer may be unrelated to the Buffer object itself.

A common issue when creating a TypedArray object that shares its memory with a Buffer is that in this case one needs to specify the byteOffset correctly:

JavaScript modules

import { Buffer } from 'node:buffer';

// Create a buffer smaller than `Buffer.poolSize`.
const nodeBuffer = Buffer.from([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);

// When casting the Node.js Buffer to an Int8Array, use the byteOffset
// to refer only to the part of `nodeBuffer.buffer` that contains the memory
// for `nodeBuffer`.
new Int8Array(nodeBuffer.buffer, nodeBuffer.byteOffset, nodeBuffer.length);

CommonJS

const { Buffer } = require('node:buffer');

// Create a buffer smaller than `Buffer.poolSize`.
const nodeBuffer = Buffer.from([0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);

// When casting the Node.js Buffer to an Int8Array, use the byteOffset
// to refer only to the part of `nodeBuffer.buffer` that contains the memory
// for `nodeBuffer`.
new Int8Array(nodeBuffer.buffer, nodeBuffer.byteOffset, nodeBuffer.length);

`buf.compare(target[, targetStart[, targetEnd[, sourceStart[, sourceEnd]]]])`

Added in: v0.11.13

History

Version	Changes
v8.0.0	The `target` parameter can now be a `Uint8Array`.
v5.11.0	Additional parameters for specifying offsets are supported now.

target <Buffer> | <Uint8Array> A Buffer or <Uint8Array> with which to compare buf.
targetStart <integer> The offset within target at which to begin comparison. Default: 0.
targetEnd <integer> The offset within target at which to end comparison (not inclusive). Default: target.length.
sourceStart <integer> The offset within buf at which to begin comparison. Default: 0.
sourceEnd <integer> The offset within buf at which to end comparison (not inclusive). Default: buf.length.
Returns: <integer>

Compares buf with target and returns a number indicating whether buf comes before, after, or is the same as target in sort order. Comparison is based on the actual sequence of bytes in each Buffer.

0 is returned if target is the same as buf
1 is returned if target should come before buf when sorted.
-1 is returned if target should come after buf when sorted.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf1 = Buffer.from('ABC');
const buf2 = Buffer.from('BCD');
const buf3 = Buffer.from('ABCD');

console.log(buf1.compare(buf1));
// Prints: 0
console.log(buf1.compare(buf2));
// Prints: -1
console.log(buf1.compare(buf3));
// Prints: -1
console.log(buf2.compare(buf1));
// Prints: 1
console.log(buf2.compare(buf3));
// Prints: 1
console.log([buf1, buf2, buf3].sort(Buffer.compare));
// Prints: [ <Buffer 41 42 43>, <Buffer 41 42 43 44>, <Buffer 42 43 44> ]
// (This result is equal to: [buf1, buf3, buf2].)

CommonJS

const { Buffer } = require('node:buffer');

const buf1 = Buffer.from('ABC');
const buf2 = Buffer.from('BCD');
const buf3 = Buffer.from('ABCD');

console.log(buf1.compare(buf1));
// Prints: 0
console.log(buf1.compare(buf2));
// Prints: -1
console.log(buf1.compare(buf3));
// Prints: -1
console.log(buf2.compare(buf1));
// Prints: 1
console.log(buf2.compare(buf3));
// Prints: 1
console.log([buf1, buf2, buf3].sort(Buffer.compare));
// Prints: [ <Buffer 41 42 43>, <Buffer 41 42 43 44>, <Buffer 42 43 44> ]
// (This result is equal to: [buf1, buf3, buf2].)

The optional targetStart, targetEnd, sourceStart, and sourceEnd arguments can be used to limit the comparison to specific ranges within target and buf respectively.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf1 = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8, 9]);
const buf2 = Buffer.from([5, 6, 7, 8, 9, 1, 2, 3, 4]);

console.log(buf1.compare(buf2, 5, 9, 0, 4));
// Prints: 0
console.log(buf1.compare(buf2, 0, 6, 4));
// Prints: -1
console.log(buf1.compare(buf2, 5, 6, 5));
// Prints: 1

CommonJS

const { Buffer } = require('node:buffer');

const buf1 = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8, 9]);
const buf2 = Buffer.from([5, 6, 7, 8, 9, 1, 2, 3, 4]);

console.log(buf1.compare(buf2, 5, 9, 0, 4));
// Prints: 0
console.log(buf1.compare(buf2, 0, 6, 4));
// Prints: -1
console.log(buf1.compare(buf2, 5, 6, 5));
// Prints: 1

ERR_OUT_OF_RANGE is thrown if targetStart < 0, sourceStart < 0, targetEnd > target.byteLength, or sourceEnd > source.byteLength.

`buf.copy(target[, targetStart[, sourceStart[, sourceEnd]]])`

Added in: v0.1.90

target <Buffer> | <Uint8Array> A Buffer or <Uint8Array> to copy into.
targetStart <integer> The offset within target at which to begin writing. Default: 0.
sourceStart <integer> The offset within buf from which to begin copying. Default: 0.
sourceEnd <integer> The offset within buf at which to stop copying (not inclusive). Default: buf.length.
Returns: <integer> The number of bytes copied.

Copies data from a region of buf to a region in target, even if the target memory region overlaps with buf.

TypedArray.prototype.set() performs the same operation, and is available for all TypedArrays, including Node.js Buffers, although it takes different function arguments.

JavaScript modules

import { Buffer } from 'node:buffer';

// Create two `Buffer` instances.
const buf1 = Buffer.allocUnsafe(26);
const buf2 = Buffer.allocUnsafe(26).fill('!');

for (let i = 0; i < 26; i++) {
  // 97 is the decimal ASCII value for 'a'.
  buf1[i] = i + 97;
}

// Copy `buf1` bytes 16 through 19 into `buf2` starting at byte 8 of `buf2`.
buf1.copy(buf2, 8, 16, 20);
// This is equivalent to:
// buf2.set(buf1.subarray(16, 20), 8);

console.log(buf2.toString('ascii', 0, 25));
// Prints: !!!!!!!!qrst!!!!!!!!!!!!!

CommonJS

const { Buffer } = require('node:buffer');

// Create two `Buffer` instances.
const buf1 = Buffer.allocUnsafe(26);
const buf2 = Buffer.allocUnsafe(26).fill('!');

for (let i = 0; i < 26; i++) {
  // 97 is the decimal ASCII value for 'a'.
  buf1[i] = i + 97;
}

// Copy `buf1` bytes 16 through 19 into `buf2` starting at byte 8 of `buf2`.
buf1.copy(buf2, 8, 16, 20);
// This is equivalent to:
// buf2.set(buf1.subarray(16, 20), 8);

console.log(buf2.toString('ascii', 0, 25));
// Prints: !!!!!!!!qrst!!!!!!!!!!!!!

JavaScript modules

import { Buffer } from 'node:buffer';

// Create a `Buffer` and copy data from one region to an overlapping region
// within the same `Buffer`.

const buf = Buffer.allocUnsafe(26);

for (let i = 0; i < 26; i++) {
  // 97 is the decimal ASCII value for 'a'.
  buf[i] = i + 97;
}

buf.copy(buf, 0, 4, 10);

console.log(buf.toString());
// Prints: efghijghijklmnopqrstuvwxyz

CommonJS

const { Buffer } = require('node:buffer');

// Create a `Buffer` and copy data from one region to an overlapping region
// within the same `Buffer`.

const buf = Buffer.allocUnsafe(26);

for (let i = 0; i < 26; i++) {
  // 97 is the decimal ASCII value for 'a'.
  buf[i] = i + 97;
}

buf.copy(buf, 0, 4, 10);

console.log(buf.toString());
// Prints: efghijghijklmnopqrstuvwxyz

`buf.entries()`

Added in: v1.1.0

Returns: <Iterator>

Creates and returns an iterator of [index, byte] pairs from the contents of buf.

JavaScript modules

import { Buffer } from 'node:buffer';

// Log the entire contents of a `Buffer`.

const buf = Buffer.from('buffer');

for (const pair of buf.entries()) {
  console.log(pair);
}
// Prints:
//   [0, 98]
//   [1, 117]
//   [2, 102]
//   [3, 102]
//   [4, 101]
//   [5, 114]

CommonJS

const { Buffer } = require('node:buffer');

// Log the entire contents of a `Buffer`.

const buf = Buffer.from('buffer');

for (const pair of buf.entries()) {
  console.log(pair);
}
// Prints:
//   [0, 98]
//   [1, 117]
//   [2, 102]
//   [3, 102]
//   [4, 101]
//   [5, 114]

`buf.equals(otherBuffer)`

Added in: v0.11.13

History

Version	Changes
v8.0.0	The arguments can now be `Uint8Array`s.

otherBuffer <Buffer> | <Uint8Array> A Buffer or <Uint8Array> with which to compare buf.
Returns: <boolean>

Returns true if both buf and otherBuffer have exactly the same bytes, false otherwise. Equivalent to buf.compare(otherBuffer) === 0.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf1 = Buffer.from('ABC');
const buf2 = Buffer.from('414243', 'hex');
const buf3 = Buffer.from('ABCD');

console.log(buf1.equals(buf2));
// Prints: true
console.log(buf1.equals(buf3));
// Prints: false

CommonJS

const { Buffer } = require('node:buffer');

const buf1 = Buffer.from('ABC');
const buf2 = Buffer.from('414243', 'hex');
const buf3 = Buffer.from('ABCD');

console.log(buf1.equals(buf2));
// Prints: true
console.log(buf1.equals(buf3));
// Prints: false

`buf.fill(value[, offset[, end]][, encoding])`

Added in: v0.5.0

History

Version	Changes
v11.0.0	Throws `ERR_OUT_OF_RANGE` instead of `ERR_INDEX_OUT_OF_RANGE`.
v10.0.0	Negative `end` values throw an `ERR_INDEX_OUT_OF_RANGE` error.
v10.0.0	Attempting to fill a non-zero length buffer with a zero length buffer triggers a thrown exception.
v10.0.0	Specifying an invalid string for `value` triggers a thrown exception.
v5.7.0	The `encoding` parameter is supported now.

value <string> | <Buffer> | <Uint8Array> | <integer> The value with which to fill buf. Empty value (string, Uint8Array, Buffer) is coerced to 0.
offset <integer> Number of bytes to skip before starting to fill buf. Default: 0.
end <integer> Where to stop filling buf (not inclusive). Default: buf.length.
encoding <string> The encoding for value if value is a string. Default: 'utf8'.
Returns: <Buffer> A reference to buf.

Fills buf with the specified value. If the offset and end are not given, the entire buf will be filled:

JavaScript modules

import { Buffer } from 'node:buffer';

// Fill a `Buffer` with the ASCII character 'h'.

const b = Buffer.allocUnsafe(50).fill('h');

console.log(b.toString());
// Prints: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

// Fill a buffer with empty string
const c = Buffer.allocUnsafe(5).fill('');

console.log(c.fill(''));
// Prints: <Buffer 00 00 00 00 00>

CommonJS

const { Buffer } = require('node:buffer');

// Fill a `Buffer` with the ASCII character 'h'.

const b = Buffer.allocUnsafe(50).fill('h');

console.log(b.toString());
// Prints: hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh

// Fill a buffer with empty string
const c = Buffer.allocUnsafe(5).fill('');

console.log(c.fill(''));
// Prints: <Buffer 00 00 00 00 00>

value is coerced to a uint32 value if it is not a string, Buffer, or integer. If the resulting integer is greater than 255 (decimal), buf will be filled with value & 255.

If the final write of a fill() operation falls on a multi-byte character, then only the bytes of that character that fit into buf are written:

JavaScript modules

import { Buffer } from 'node:buffer';

// Fill a `Buffer` with character that takes up two bytes in UTF-8.

console.log(Buffer.allocUnsafe(5).fill('\u0222'));
// Prints: <Buffer c8 a2 c8 a2 c8>

CommonJS

const { Buffer } = require('node:buffer');

// Fill a `Buffer` with character that takes up two bytes in UTF-8.

console.log(Buffer.allocUnsafe(5).fill('\u0222'));
// Prints: <Buffer c8 a2 c8 a2 c8>

If value contains invalid characters, it is truncated; if no valid fill data remains, an exception is thrown:

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(5);

console.log(buf.fill('a'));
// Prints: <Buffer 61 61 61 61 61>
console.log(buf.fill('aazz', 'hex'));
// Prints: <Buffer aa aa aa aa aa>
console.log(buf.fill('zz', 'hex'));
// Throws an exception.

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(5);

console.log(buf.fill('a'));
// Prints: <Buffer 61 61 61 61 61>
console.log(buf.fill('aazz', 'hex'));
// Prints: <Buffer aa aa aa aa aa>
console.log(buf.fill('zz', 'hex'));
// Throws an exception.

`buf.includes(value[, start[, end]][, encoding])`

Added in: v5.3.0

History

Version	Changes
v26.1.0	Added the `end` parameter.
v25.5.0, v24.13.1	supports Uint8Array as `this` value.

value <string> | <Buffer> | <Uint8Array> | <integer> What to search for.
start <integer> Where to begin searching in buf. If negative, then offset is calculated from the end of buf. Default: 0.
end <integer> Where to stop searching in buf (exclusive). Default: buf.length.
encoding <string> If value is a string, this is its encoding. Default: 'utf8'.
Returns: <boolean> true if value was found in buf, false otherwise.

Equivalent to buf.indexOf() !== -1.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from('this is a buffer');

console.log(buf.includes('this'));
// Prints: true
console.log(buf.includes('is'));
// Prints: true
console.log(buf.includes(Buffer.from('a buffer')));
// Prints: true
console.log(buf.includes(97));
// Prints: true (97 is the decimal ASCII value for 'a')
console.log(buf.includes(Buffer.from('a buffer example')));
// Prints: false
console.log(buf.includes(Buffer.from('a buffer example').slice(0, 8)));
// Prints: true
console.log(buf.includes('this', 4));
// Prints: false

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from('this is a buffer');

console.log(buf.includes('this'));
// Prints: true
console.log(buf.includes('is'));
// Prints: true
console.log(buf.includes(Buffer.from('a buffer')));
// Prints: true
console.log(buf.includes(97));
// Prints: true (97 is the decimal ASCII value for 'a')
console.log(buf.includes(Buffer.from('a buffer example')));
// Prints: false
console.log(buf.includes(Buffer.from('a buffer example').slice(0, 8)));
// Prints: true
console.log(buf.includes('this', 4));
// Prints: false

`buf.indexOf(value[, start[, end]][, encoding])`

Added in: v1.5.0

History

Version	Changes
v26.1.0	Added the `end` parameter.
v8.0.0	The `value` can now be a `Uint8Array`.
v5.7.0, v4.4.0	When `encoding` is being passed, the `byteOffset` parameter is no longer required.

value <string> | <Buffer> | <Uint8Array> | <integer> What to search for.
start <integer> Where to begin searching in buf. If negative, then offset is calculated from the end of buf. Default: 0.
end <integer> Where to stop searching in buf (exclusive). Default: buf.length.
encoding <string> If value is a string, this is the encoding used to determine the binary representation of the string that will be searched for in buf. Default: 'utf8'.
Returns: <integer> The index of the first occurrence of value in buf, or -1 if buf does not contain value.

If value is:

a string, value is interpreted according to the character encoding in encoding.
a Buffer or <Uint8Array>, value will be used in its entirety. To compare a partial Buffer, use buf.subarray.
a number, value will be interpreted as an unsigned 8-bit integer value between 0 and 255.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from('this is a buffer');

console.log(buf.indexOf('this'));
// Prints: 0
console.log(buf.indexOf('is'));
// Prints: 2
console.log(buf.indexOf(Buffer.from('a buffer')));
// Prints: 8
console.log(buf.indexOf(97));
// Prints: 8 (97 is the decimal ASCII value for 'a')
console.log(buf.indexOf(Buffer.from('a buffer example')));
// Prints: -1
console.log(buf.indexOf(Buffer.from('a buffer example').slice(0, 8)));
// Prints: 8

const utf16Buffer = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'utf16le');

console.log(utf16Buffer.indexOf('\u03a3', 0, 'utf16le'));
// Prints: 4
console.log(utf16Buffer.indexOf('\u03a3', -4, 'utf16le'));
// Prints: 6

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from('this is a buffer');

console.log(buf.indexOf('this'));
// Prints: 0
console.log(buf.indexOf('is'));
// Prints: 2
console.log(buf.indexOf(Buffer.from('a buffer')));
// Prints: 8
console.log(buf.indexOf(97));
// Prints: 8 (97 is the decimal ASCII value for 'a')
console.log(buf.indexOf(Buffer.from('a buffer example')));
// Prints: -1
console.log(buf.indexOf(Buffer.from('a buffer example').slice(0, 8)));
// Prints: 8

const utf16Buffer = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'utf16le');

console.log(utf16Buffer.indexOf('\u03a3', 0, 'utf16le'));
// Prints: 4
console.log(utf16Buffer.indexOf('\u03a3', -4, 'utf16le'));
// Prints: 6

If value is not a string, number, or Buffer, this method will throw a TypeError. If value is a number, it will be coerced to a valid byte value, an integer between 0 and 255.

If byteOffset is not a number, it will be coerced to a number. If the result of coercion is NaN or 0, then the entire buffer will be searched. This behavior matches String.prototype.indexOf().

JavaScript modules

import { Buffer } from 'node:buffer';

const b = Buffer.from('abcdef');

// Passing a value that's a number, but not a valid byte.
// Prints: 2, equivalent to searching for 99 or 'c'.
console.log(b.indexOf(99.9));
console.log(b.indexOf(256 + 99));

// Passing a byteOffset that coerces to NaN or 0.
// Prints: 1, searching the whole buffer.
console.log(b.indexOf('b', undefined));
console.log(b.indexOf('b', {}));
console.log(b.indexOf('b', null));
console.log(b.indexOf('b', []));

CommonJS

const { Buffer } = require('node:buffer');

const b = Buffer.from('abcdef');

// Passing a value that's a number, but not a valid byte.
// Prints: 2, equivalent to searching for 99 or 'c'.
console.log(b.indexOf(99.9));
console.log(b.indexOf(256 + 99));

// Passing a byteOffset that coerces to NaN or 0.
// Prints: 1, searching the whole buffer.
console.log(b.indexOf('b', undefined));
console.log(b.indexOf('b', {}));
console.log(b.indexOf('b', null));
console.log(b.indexOf('b', []));

If value is an empty string or empty Buffer and byteOffset is less than buf.length, byteOffset will be returned. If value is empty and byteOffset is at least buf.length, buf.length will be returned.

`buf.keys()`

Added in: v1.1.0

Returns: <Iterator>

Creates and returns an iterator of buf keys (indexes).

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from('buffer');

for (const key of buf.keys()) {
  console.log(key);
}
// Prints:
//   0
//   1
//   2
//   3
//   4
//   5

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from('buffer');

for (const key of buf.keys()) {
  console.log(key);
}
// Prints:
//   0
//   1
//   2
//   3
//   4
//   5

`buf.lastIndexOf(value[, start[, end]][, encoding])`

Added in: v6.0.0

History

Version	Changes
v26.1.0	Added the `end` parameter.
v8.0.0	The `value` can now be a `Uint8Array`.

value <string> | <Buffer> | <Uint8Array> | <integer> What to search for.
start <integer> Where to begin searching in buf. If negative, then offset is calculated from the end of buf. Default: buf.length - 1.
end <integer> Where to stop searching in buf (exclusive). Default: buf.length.
encoding <string> If value is a string, this is the encoding used to determine the binary representation of the string that will be searched for in buf. Default: 'utf8'.
Returns: <integer> The index of the last occurrence of value in buf, or -1 if buf does not contain value.

Identical to buf.indexOf(), except the last occurrence of value is found rather than the first occurrence.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from('this buffer is a buffer');

console.log(buf.lastIndexOf('this'));
// Prints: 0
console.log(buf.lastIndexOf('buffer'));
// Prints: 17
console.log(buf.lastIndexOf(Buffer.from('buffer')));
// Prints: 17
console.log(buf.lastIndexOf(97));
// Prints: 15 (97 is the decimal ASCII value for 'a')
console.log(buf.lastIndexOf(Buffer.from('yolo')));
// Prints: -1
console.log(buf.lastIndexOf('buffer', 5));
// Prints: 5
console.log(buf.lastIndexOf('buffer', 4));
// Prints: -1

const utf16Buffer = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'utf16le');

console.log(utf16Buffer.lastIndexOf('\u03a3', undefined, 'utf16le'));
// Prints: 6
console.log(utf16Buffer.lastIndexOf('\u03a3', -5, 'utf16le'));
// Prints: 4

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from('this buffer is a buffer');

console.log(buf.lastIndexOf('this'));
// Prints: 0
console.log(buf.lastIndexOf('buffer'));
// Prints: 17
console.log(buf.lastIndexOf(Buffer.from('buffer')));
// Prints: 17
console.log(buf.lastIndexOf(97));
// Prints: 15 (97 is the decimal ASCII value for 'a')
console.log(buf.lastIndexOf(Buffer.from('yolo')));
// Prints: -1
console.log(buf.lastIndexOf('buffer', 5));
// Prints: 5
console.log(buf.lastIndexOf('buffer', 4));
// Prints: -1

const utf16Buffer = Buffer.from('\u039a\u0391\u03a3\u03a3\u0395', 'utf16le');

console.log(utf16Buffer.lastIndexOf('\u03a3', undefined, 'utf16le'));
// Prints: 6
console.log(utf16Buffer.lastIndexOf('\u03a3', -5, 'utf16le'));
// Prints: 4

If value is not a string, number, or Buffer, this method will throw a TypeError. If value is a number, it will be coerced to a valid byte value, an integer between 0 and 255.

If byteOffset is not a number, it will be coerced to a number. Any arguments that coerce to NaN, like {} or undefined, will search the whole buffer. This behavior matches String.prototype.lastIndexOf().

JavaScript modules

import { Buffer } from 'node:buffer';

const b = Buffer.from('abcdef');

// Passing a value that's a number, but not a valid byte.
// Prints: 2, equivalent to searching for 99 or 'c'.
console.log(b.lastIndexOf(99.9));
console.log(b.lastIndexOf(256 + 99));

// Passing a byteOffset that coerces to NaN.
// Prints: 1, searching the whole buffer.
console.log(b.lastIndexOf('b', undefined));
console.log(b.lastIndexOf('b', {}));

// Passing a byteOffset that coerces to 0.
// Prints: -1, equivalent to passing 0.
console.log(b.lastIndexOf('b', null));
console.log(b.lastIndexOf('b', []));

CommonJS

const { Buffer } = require('node:buffer');

const b = Buffer.from('abcdef');

// Passing a value that's a number, but not a valid byte.
// Prints: 2, equivalent to searching for 99 or 'c'.
console.log(b.lastIndexOf(99.9));
console.log(b.lastIndexOf(256 + 99));

// Passing a byteOffset that coerces to NaN.
// Prints: 1, searching the whole buffer.
console.log(b.lastIndexOf('b', undefined));
console.log(b.lastIndexOf('b', {}));

// Passing a byteOffset that coerces to 0.
// Prints: -1, equivalent to passing 0.
console.log(b.lastIndexOf('b', null));
console.log(b.lastIndexOf('b', []));

If value is an empty string or empty Buffer, byteOffset will be returned.

`buf.length`

Added in: v0.1.90

Type: <integer>

Returns the number of bytes in buf.

JavaScript modules

import { Buffer } from 'node:buffer';

// Create a `Buffer` and write a shorter string to it using UTF-8.

const buf = Buffer.alloc(1234);

console.log(buf.length);
// Prints: 1234

buf.write('some string', 0, 'utf8');

console.log(buf.length);
// Prints: 1234

CommonJS

const { Buffer } = require('node:buffer');

// Create a `Buffer` and write a shorter string to it using UTF-8.

const buf = Buffer.alloc(1234);

console.log(buf.length);
// Prints: 1234

buf.write('some string', 0, 'utf8');

console.log(buf.length);
// Prints: 1234

`buf.parent`

Deprecated in: v8.0.0

Stability: 0 - Deprecated: Use buf.buffer instead.

The buf.parent property is a deprecated alias for buf.buffer.

`buf.readBigInt64BE([offset])`

Added in: v12.0.0, v10.20.0

offset <integer> Number of bytes to skip before starting to read. Must satisfy: 0 <= offset <= buf.length - 8. Default: 0.
Returns: <bigint>

Reads a signed, big-endian 64-bit integer from buf at the specified offset.

Integers read from a Buffer are interpreted as two's complement signed values.

`buf.readBigInt64LE([offset])`

Added in: v12.0.0, v10.20.0

offset <integer> Number of bytes to skip before starting to read. Must satisfy: 0 <= offset <= buf.length - 8. Default: 0.
Returns: <bigint>

Reads a signed, little-endian 64-bit integer from buf at the specified offset.

Integers read from a Buffer are interpreted as two's complement signed values.

`buf.readBigUInt64BE([offset])`

Added in: v12.0.0, v10.20.0

History

Version	Changes
v14.10.0, v12.19.0	This function is also available as `buf.readBigUint64BE()`.

offset <integer> Number of bytes to skip before starting to read. Must satisfy: 0 <= offset <= buf.length - 8. Default: 0.
Returns: <bigint>

Reads an unsigned, big-endian 64-bit integer from buf at the specified offset.

This function is also available under the readBigUint64BE alias.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff]);

console.log(buf.readBigUInt64BE(0));
// Prints: 4294967295n

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff]);

console.log(buf.readBigUInt64BE(0));
// Prints: 4294967295n

`buf.readBigUInt64LE([offset])`

Added in: v12.0.0, v10.20.0

History

Version	Changes
v14.10.0, v12.19.0	This function is also available as `buf.readBigUint64LE()`.

offset <integer> Number of bytes to skip before starting to read. Must satisfy: 0 <= offset <= buf.length - 8. Default: 0.
Returns: <bigint>

Reads an unsigned, little-endian 64-bit integer from buf at the specified offset.

This function is also available under the readBigUint64LE alias.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff]);

console.log(buf.readBigUInt64LE(0));
// Prints: 18446744069414584320n

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xff, 0xff]);

console.log(buf.readBigUInt64LE(0));
// Prints: 18446744069414584320n

`buf.readDoubleBE([offset])`

Added in: v0.11.15

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 8. Default: 0.
Returns: <number>

Reads a 64-bit, big-endian double from buf at the specified offset.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);

console.log(buf.readDoubleBE(0));
// Prints: 8.20788039913184e-304

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);

console.log(buf.readDoubleBE(0));
// Prints: 8.20788039913184e-304

`buf.readDoubleLE([offset])`

Added in: v0.11.15

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 8. Default: 0.
Returns: <number>

Reads a 64-bit, little-endian double from buf at the specified offset.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);

console.log(buf.readDoubleLE(0));
// Prints: 5.447603722011605e-270
console.log(buf.readDoubleLE(1));
// Throws ERR_OUT_OF_RANGE.

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([1, 2, 3, 4, 5, 6, 7, 8]);

console.log(buf.readDoubleLE(0));
// Prints: 5.447603722011605e-270
console.log(buf.readDoubleLE(1));
// Throws ERR_OUT_OF_RANGE.

`buf.readFloatBE([offset])`

Added in: v0.11.15

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4. Default: 0.
Returns: <number>

Reads a 32-bit, big-endian float from buf at the specified offset.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([1, 2, 3, 4]);

console.log(buf.readFloatBE(0));
// Prints: 2.387939260590663e-38

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([1, 2, 3, 4]);

console.log(buf.readFloatBE(0));
// Prints: 2.387939260590663e-38

`buf.readFloatLE([offset])`

Added in: v0.11.15

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4. Default: 0.
Returns: <number>

Reads a 32-bit, little-endian float from buf at the specified offset.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([1, 2, 3, 4]);

console.log(buf.readFloatLE(0));
// Prints: 1.539989614439558e-36
console.log(buf.readFloatLE(1));
// Throws ERR_OUT_OF_RANGE.

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([1, 2, 3, 4]);

console.log(buf.readFloatLE(0));
// Prints: 1.539989614439558e-36
console.log(buf.readFloatLE(1));
// Throws ERR_OUT_OF_RANGE.

`buf.readInt8([offset])`

Added in: v0.5.0

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 1. Default: 0.
Returns: <integer>

Reads a signed 8-bit integer from buf at the specified offset.

Integers read from a Buffer are interpreted as two's complement signed values.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([-1, 5]);

console.log(buf.readInt8(0));
// Prints: -1
console.log(buf.readInt8(1));
// Prints: 5
console.log(buf.readInt8(2));
// Throws ERR_OUT_OF_RANGE.

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([-1, 5]);

console.log(buf.readInt8(0));
// Prints: -1
console.log(buf.readInt8(1));
// Prints: 5
console.log(buf.readInt8(2));
// Throws ERR_OUT_OF_RANGE.

`buf.readInt16BE([offset])`

Added in: v0.5.5

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 2. Default: 0.
Returns: <integer>

Reads a signed, big-endian 16-bit integer from buf at the specified offset.

Integers read from a Buffer are interpreted as two's complement signed values.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([0, 5]);

console.log(buf.readInt16BE(0));
// Prints: 5

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([0, 5]);

console.log(buf.readInt16BE(0));
// Prints: 5

`buf.readInt16LE([offset])`

Added in: v0.5.5

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 2. Default: 0.
Returns: <integer>

Reads a signed, little-endian 16-bit integer from buf at the specified offset.

Integers read from a Buffer are interpreted as two's complement signed values.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([0, 5]);

console.log(buf.readInt16LE(0));
// Prints: 1280
console.log(buf.readInt16LE(1));
// Throws ERR_OUT_OF_RANGE.

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([0, 5]);

console.log(buf.readInt16LE(0));
// Prints: 1280
console.log(buf.readInt16LE(1));
// Throws ERR_OUT_OF_RANGE.

`buf.readInt32BE([offset])`

Added in: v0.5.5

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4. Default: 0.
Returns: <integer>

Reads a signed, big-endian 32-bit integer from buf at the specified offset.

Integers read from a Buffer are interpreted as two's complement signed values.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([0, 0, 0, 5]);

console.log(buf.readInt32BE(0));
// Prints: 5

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([0, 0, 0, 5]);

console.log(buf.readInt32BE(0));
// Prints: 5

`buf.readInt32LE([offset])`

Added in: v0.5.5

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4. Default: 0.
Returns: <integer>

Reads a signed, little-endian 32-bit integer from buf at the specified offset.

Integers read from a Buffer are interpreted as two's complement signed values.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([0, 0, 0, 5]);

console.log(buf.readInt32LE(0));
// Prints: 83886080
console.log(buf.readInt32LE(1));
// Throws ERR_OUT_OF_RANGE.

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([0, 0, 0, 5]);

console.log(buf.readInt32LE(0));
// Prints: 83886080
console.log(buf.readInt32LE(1));
// Throws ERR_OUT_OF_RANGE.

`buf.readIntBE(offset, byteLength)`

Added in: v0.11.15

History

Version	Changes
v25.5.0, v24.13.1	supports Uint8Array as `this` value.
v10.0.0	Removed `noAssert` and no implicit coercion of the offset and `byteLength` to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - byteLength.
byteLength <integer> Number of bytes to read. Must satisfy 0 < byteLength <= 6.
Returns: <integer>

Reads byteLength number of bytes from buf at the specified offset and interprets the result as a big-endian, two's complement signed value supporting up to 48 bits of accuracy.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);

console.log(buf.readIntBE(0, 6).toString(16));
// Prints: 1234567890ab
console.log(buf.readIntBE(1, 6).toString(16));
// Throws ERR_OUT_OF_RANGE.
console.log(buf.readIntBE(1, 0).toString(16));
// Throws ERR_OUT_OF_RANGE.

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);

console.log(buf.readIntBE(0, 6).toString(16));
// Prints: 1234567890ab
console.log(buf.readIntBE(1, 6).toString(16));
// Throws ERR_OUT_OF_RANGE.
console.log(buf.readIntBE(1, 0).toString(16));
// Throws ERR_OUT_OF_RANGE.

`buf.readIntLE(offset, byteLength)`

Added in: v0.11.15

History

Version	Changes
v25.5.0, v24.13.1	supports Uint8Array as `this` value.
v10.0.0	Removed `noAssert` and no implicit coercion of the offset and `byteLength` to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - byteLength.
byteLength <integer> Number of bytes to read. Must satisfy 0 < byteLength <= 6.
Returns: <integer>

Reads byteLength number of bytes from buf at the specified offset and interprets the result as a little-endian, two's complement signed value supporting up to 48 bits of accuracy.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);

console.log(buf.readIntLE(0, 6).toString(16));
// Prints: -546f87a9cbee

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);

console.log(buf.readIntLE(0, 6).toString(16));
// Prints: -546f87a9cbee

`buf.readUInt8([offset])`

Added in: v0.5.0

History

Version	Changes
v14.9.0, v12.19.0	This function is also available as `buf.readUint8()`.
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 1. Default: 0.
Returns: <integer>

Reads an unsigned 8-bit integer from buf at the specified offset.

This function is also available under the readUint8 alias.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([1, -2]);

console.log(buf.readUInt8(0));
// Prints: 1
console.log(buf.readUInt8(1));
// Prints: 254
console.log(buf.readUInt8(2));
// Throws ERR_OUT_OF_RANGE.

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([1, -2]);

console.log(buf.readUInt8(0));
// Prints: 1
console.log(buf.readUInt8(1));
// Prints: 254
console.log(buf.readUInt8(2));
// Throws ERR_OUT_OF_RANGE.

`buf.readUInt16BE([offset])`

Added in: v0.5.5

History

Version	Changes
v14.9.0, v12.19.0	This function is also available as `buf.readUint16BE()`.
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 2. Default: 0.
Returns: <integer>

Reads an unsigned, big-endian 16-bit integer from buf at the specified offset.

This function is also available under the readUint16BE alias.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x12, 0x34, 0x56]);

console.log(buf.readUInt16BE(0).toString(16));
// Prints: 1234
console.log(buf.readUInt16BE(1).toString(16));
// Prints: 3456

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([0x12, 0x34, 0x56]);

console.log(buf.readUInt16BE(0).toString(16));
// Prints: 1234
console.log(buf.readUInt16BE(1).toString(16));
// Prints: 3456

`buf.readUInt16LE([offset])`

Added in: v0.5.5

History

Version	Changes
v14.9.0, v12.19.0	This function is also available as `buf.readUint16LE()`.
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 2. Default: 0.
Returns: <integer>

Reads an unsigned, little-endian 16-bit integer from buf at the specified offset.

This function is also available under the readUint16LE alias.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x12, 0x34, 0x56]);

console.log(buf.readUInt16LE(0).toString(16));
// Prints: 3412
console.log(buf.readUInt16LE(1).toString(16));
// Prints: 5634
console.log(buf.readUInt16LE(2).toString(16));
// Throws ERR_OUT_OF_RANGE.

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([0x12, 0x34, 0x56]);

console.log(buf.readUInt16LE(0).toString(16));
// Prints: 3412
console.log(buf.readUInt16LE(1).toString(16));
// Prints: 5634
console.log(buf.readUInt16LE(2).toString(16));
// Throws ERR_OUT_OF_RANGE.

`buf.readUInt32BE([offset])`

Added in: v0.5.5

History

Version	Changes
v14.9.0, v12.19.0	This function is also available as `buf.readUint32BE()`.
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4. Default: 0.
Returns: <integer>

Reads an unsigned, big-endian 32-bit integer from buf at the specified offset.

This function is also available under the readUint32BE alias.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);

console.log(buf.readUInt32BE(0).toString(16));
// Prints: 12345678

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);

console.log(buf.readUInt32BE(0).toString(16));
// Prints: 12345678

`buf.readUInt32LE([offset])`

Added in: v0.5.5

History

Version	Changes
v14.9.0, v12.19.0	This function is also available as `buf.readUint32LE()`.
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - 4. Default: 0.
Returns: <integer>

Reads an unsigned, little-endian 32-bit integer from buf at the specified offset.

This function is also available under the readUint32LE alias.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);

console.log(buf.readUInt32LE(0).toString(16));
// Prints: 78563412
console.log(buf.readUInt32LE(1).toString(16));
// Throws ERR_OUT_OF_RANGE.

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78]);

console.log(buf.readUInt32LE(0).toString(16));
// Prints: 78563412
console.log(buf.readUInt32LE(1).toString(16));
// Throws ERR_OUT_OF_RANGE.

`buf.readUIntBE(offset, byteLength)`

Added in: v0.11.15

History

Version	Changes
v25.5.0, v24.13.1	supports Uint8Array as `this` value.
v14.9.0, v12.19.0	This function is also available as `buf.readUintBE()`.
v10.0.0	Removed `noAssert` and no implicit coercion of the offset and `byteLength` to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - byteLength.
byteLength <integer> Number of bytes to read. Must satisfy 0 < byteLength <= 6.
Returns: <integer>

Reads byteLength number of bytes from buf at the specified offset and interprets the result as an unsigned big-endian integer supporting up to 48 bits of accuracy.

This function is also available under the readUintBE alias.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);

console.log(buf.readUIntBE(0, 6).toString(16));
// Prints: 1234567890ab
console.log(buf.readUIntBE(1, 6).toString(16));
// Throws ERR_OUT_OF_RANGE.

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);

console.log(buf.readUIntBE(0, 6).toString(16));
// Prints: 1234567890ab
console.log(buf.readUIntBE(1, 6).toString(16));
// Throws ERR_OUT_OF_RANGE.

`buf.readUIntLE(offset, byteLength)`

Added in: v0.11.15

History

Version	Changes
v25.5.0, v24.13.1	supports Uint8Array as `this` value.
v14.9.0, v12.19.0	This function is also available as `buf.readUintLE()`.
v10.0.0	Removed `noAssert` and no implicit coercion of the offset and `byteLength` to `uint32` anymore.

offset <integer> Number of bytes to skip before starting to read. Must satisfy 0 <= offset <= buf.length - byteLength.
byteLength <integer> Number of bytes to read. Must satisfy 0 < byteLength <= 6.
Returns: <integer>

Reads byteLength number of bytes from buf at the specified offset and interprets the result as an unsigned, little-endian integer supporting up to 48 bits of accuracy.

This function is also available under the readUintLE alias.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);

console.log(buf.readUIntLE(0, 6).toString(16));
// Prints: ab9078563412

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([0x12, 0x34, 0x56, 0x78, 0x90, 0xab]);

console.log(buf.readUIntLE(0, 6).toString(16));
// Prints: ab9078563412

`buf.subarray([start[, end]])`

Added in: v3.0.0

start <integer> Where the new Buffer will start. Default: 0.
end <integer> Where the new Buffer will end (not inclusive). Default: buf.length.
Returns: <Buffer>

Returns a new Buffer that references the same memory as the original, but offset and cropped by the start and end indexes.

Specifying end greater than buf.length will return the same result as that of end equal to buf.length.

This method is inherited from TypedArray.prototype.subarray().

Modifying the new Buffer slice will modify the memory in the original Buffer because the allocated memory of the two objects overlap.

JavaScript modules

import { Buffer } from 'node:buffer';

// Create a `Buffer` with the ASCII alphabet, take a slice, and modify one byte
// from the original `Buffer`.

const buf1 = Buffer.allocUnsafe(26);

for (let i = 0; i < 26; i++) {
  // 97 is the decimal ASCII value for 'a'.
  buf1[i] = i + 97;
}

const buf2 = buf1.subarray(0, 3);

console.log(buf2.toString('ascii', 0, buf2.length));
// Prints: abc

buf1[0] = 33;

console.log(buf2.toString('ascii', 0, buf2.length));
// Prints: !bc

CommonJS

const { Buffer } = require('node:buffer');

// Create a `Buffer` with the ASCII alphabet, take a slice, and modify one byte
// from the original `Buffer`.

const buf1 = Buffer.allocUnsafe(26);

for (let i = 0; i < 26; i++) {
  // 97 is the decimal ASCII value for 'a'.
  buf1[i] = i + 97;
}

const buf2 = buf1.subarray(0, 3);

console.log(buf2.toString('ascii', 0, buf2.length));
// Prints: abc

buf1[0] = 33;

console.log(buf2.toString('ascii', 0, buf2.length));
// Prints: !bc

Specifying negative indexes causes the slice to be generated relative to the end of buf rather than the beginning.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from('buffer');

console.log(buf.subarray(-6, -1).toString());
// Prints: buffe
// (Equivalent to buf.subarray(0, 5).)

console.log(buf.subarray(-6, -2).toString());
// Prints: buff
// (Equivalent to buf.subarray(0, 4).)

console.log(buf.subarray(-5, -2).toString());
// Prints: uff
// (Equivalent to buf.subarray(1, 4).)

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from('buffer');

console.log(buf.subarray(-6, -1).toString());
// Prints: buffe
// (Equivalent to buf.subarray(0, 5).)

console.log(buf.subarray(-6, -2).toString());
// Prints: buff
// (Equivalent to buf.subarray(0, 4).)

console.log(buf.subarray(-5, -2).toString());
// Prints: uff
// (Equivalent to buf.subarray(1, 4).)

`buf.slice([start[, end]])`

Added in: v0.3.0

History

Version	Changes
v17.5.0, v16.15.0	The buf.slice() method has been deprecated.
v7.1.0, v6.9.2	Coercing the offsets to integers now handles values outside the 32-bit integer range properly.
v7.0.0	All offsets are now coerced to integers before doing any calculations with them.

Stability: 0 - Deprecated: Use buf.subarray instead.

start <integer> Where the new Buffer will start. Default: 0.
end <integer> Where the new Buffer will end (not inclusive). Default: buf.length.
Returns: <Buffer>

Returns a new Buffer that references the same memory as the original, but offset and cropped by the start and end indexes.

This method is not compatible with the Uint8Array.prototype.slice(), which is a superclass of Buffer. To copy the slice, use Uint8Array.prototype.slice().

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from('buffer');

const copiedBuf = Uint8Array.prototype.slice.call(buf);
copiedBuf[0]++;
console.log(copiedBuf.toString());
// Prints: cuffer

console.log(buf.toString());
// Prints: buffer

// With buf.slice(), the original buffer is modified.
const notReallyCopiedBuf = buf.slice();
notReallyCopiedBuf[0]++;
console.log(notReallyCopiedBuf.toString());
// Prints: cuffer
console.log(buf.toString());
// Also prints: cuffer (!)

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from('buffer');

const copiedBuf = Uint8Array.prototype.slice.call(buf);
copiedBuf[0]++;
console.log(copiedBuf.toString());
// Prints: cuffer

console.log(buf.toString());
// Prints: buffer

// With buf.slice(), the original buffer is modified.
const notReallyCopiedBuf = buf.slice();
notReallyCopiedBuf[0]++;
console.log(notReallyCopiedBuf.toString());
// Prints: cuffer
console.log(buf.toString());
// Also prints: cuffer (!)

`buf.swap16()`

Added in: v5.10.0

Returns: <Buffer> A reference to buf.

Interprets buf as an array of unsigned 16-bit integers and swaps the byte order in-place. Throws ERR_INVALID_BUFFER_SIZE if buf.length is not a multiple of 2.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);

console.log(buf1);
// Prints: <Buffer 01 02 03 04 05 06 07 08>

buf1.swap16();

console.log(buf1);
// Prints: <Buffer 02 01 04 03 06 05 08 07>

const buf2 = Buffer.from([0x1, 0x2, 0x3]);

buf2.swap16();
// Throws ERR_INVALID_BUFFER_SIZE.

CommonJS

const { Buffer } = require('node:buffer');

const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);

console.log(buf1);
// Prints: <Buffer 01 02 03 04 05 06 07 08>

buf1.swap16();

console.log(buf1);
// Prints: <Buffer 02 01 04 03 06 05 08 07>

const buf2 = Buffer.from([0x1, 0x2, 0x3]);

buf2.swap16();
// Throws ERR_INVALID_BUFFER_SIZE.

One convenient use of buf.swap16() is to perform a fast in-place conversion between UTF-16 little-endian and UTF-16 big-endian:

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from('This is little-endian UTF-16', 'utf16le');
buf.swap16(); // Convert to big-endian UTF-16 text.

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from('This is little-endian UTF-16', 'utf16le');
buf.swap16(); // Convert to big-endian UTF-16 text.

`buf.swap32()`

Added in: v5.10.0

Returns: <Buffer> A reference to buf.

Interprets buf as an array of unsigned 32-bit integers and swaps the byte order in-place. Throws ERR_INVALID_BUFFER_SIZE if buf.length is not a multiple of 4.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);

console.log(buf1);
// Prints: <Buffer 01 02 03 04 05 06 07 08>

buf1.swap32();

console.log(buf1);
// Prints: <Buffer 04 03 02 01 08 07 06 05>

const buf2 = Buffer.from([0x1, 0x2, 0x3]);

buf2.swap32();
// Throws ERR_INVALID_BUFFER_SIZE.

CommonJS

const { Buffer } = require('node:buffer');

const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);

console.log(buf1);
// Prints: <Buffer 01 02 03 04 05 06 07 08>

buf1.swap32();

console.log(buf1);
// Prints: <Buffer 04 03 02 01 08 07 06 05>

const buf2 = Buffer.from([0x1, 0x2, 0x3]);

buf2.swap32();
// Throws ERR_INVALID_BUFFER_SIZE.

`buf.swap64()`

Added in: v6.3.0

Returns: <Buffer> A reference to buf.

Interprets buf as an array of 64-bit numbers and swaps byte order in-place. Throws ERR_INVALID_BUFFER_SIZE if buf.length is not a multiple of 8.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);

console.log(buf1);
// Prints: <Buffer 01 02 03 04 05 06 07 08>

buf1.swap64();

console.log(buf1);
// Prints: <Buffer 08 07 06 05 04 03 02 01>

const buf2 = Buffer.from([0x1, 0x2, 0x3]);

buf2.swap64();
// Throws ERR_INVALID_BUFFER_SIZE.

CommonJS

const { Buffer } = require('node:buffer');

const buf1 = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0x7, 0x8]);

console.log(buf1);
// Prints: <Buffer 01 02 03 04 05 06 07 08>

buf1.swap64();

console.log(buf1);
// Prints: <Buffer 08 07 06 05 04 03 02 01>

const buf2 = Buffer.from([0x1, 0x2, 0x3]);

buf2.swap64();
// Throws ERR_INVALID_BUFFER_SIZE.

`buf.toJSON()`

Added in: v0.9.2

Returns: <Object>

Returns a JSON representation of buf. JSON.stringify() implicitly calls this function when stringifying a Buffer instance.

Buffer.from() accepts objects in the format returned from this method. In particular, Buffer.from(buf.toJSON()) works like Buffer.from(buf).

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5]);
const json = JSON.stringify(buf);

console.log(json);
// Prints: {"type":"Buffer","data":[1,2,3,4,5]}

const copy = JSON.parse(json, (key, value) => {
  return value && value.type === 'Buffer' ?
    Buffer.from(value) :
    value;
});

console.log(copy);
// Prints: <Buffer 01 02 03 04 05>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from([0x1, 0x2, 0x3, 0x4, 0x5]);
const json = JSON.stringify(buf);

console.log(json);
// Prints: {"type":"Buffer","data":[1,2,3,4,5]}

const copy = JSON.parse(json, (key, value) => {
  return value && value.type === 'Buffer' ?
    Buffer.from(value) :
    value;
});

console.log(copy);
// Prints: <Buffer 01 02 03 04 05>

`buf.toString([encoding[, start[, end]]])`

Added in: v0.1.90

History

Version	Changes
v25.5.0, v24.13.1	supports Uint8Array as `this` value.

encoding <string> The character encoding to use. Default: 'utf8'.
start <integer> The byte offset to start decoding at. Default: 0.
end <integer> The byte offset to stop decoding at (not inclusive). Default: buf.length.
Returns: <string>

Decodes buf to a string according to the specified character encoding in encoding. start and end may be passed to decode only a subset of buf.

If encoding is 'utf8' and a byte sequence in the input is not valid UTF-8, then each invalid byte is replaced with the replacement character U+FFFD.

The maximum length of a string instance (in UTF-16 code units) is available as buffer.constants.MAX_STRING_LENGTH.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf1 = Buffer.allocUnsafe(26);

for (let i = 0; i < 26; i++) {
  // 97 is the decimal ASCII value for 'a'.
  buf1[i] = i + 97;
}

console.log(buf1.toString('utf8'));
// Prints: abcdefghijklmnopqrstuvwxyz
console.log(buf1.toString('utf8', 0, 5));
// Prints: abcde

const buf2 = Buffer.from('tést');

console.log(buf2.toString('hex'));
// Prints: 74c3a97374
console.log(buf2.toString('utf8', 0, 3));
// Prints: té
console.log(buf2.toString(undefined, 0, 3));
// Prints: té

CommonJS

const { Buffer } = require('node:buffer');

const buf1 = Buffer.allocUnsafe(26);

for (let i = 0; i < 26; i++) {
  // 97 is the decimal ASCII value for 'a'.
  buf1[i] = i + 97;
}

console.log(buf1.toString('utf8'));
// Prints: abcdefghijklmnopqrstuvwxyz
console.log(buf1.toString('utf8', 0, 5));
// Prints: abcde

const buf2 = Buffer.from('tést');

console.log(buf2.toString('hex'));
// Prints: 74c3a97374
console.log(buf2.toString('utf8', 0, 3));
// Prints: té
console.log(buf2.toString(undefined, 0, 3));
// Prints: té

`buf.values()`

Added in: v1.1.0

Returns: <Iterator>

Creates and returns an iterator for buf values (bytes). This function is called automatically when a Buffer is used in a for..of statement.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.from('buffer');

for (const value of buf.values()) {
  console.log(value);
}
// Prints:
//   98
//   117
//   102
//   102
//   101
//   114

for (const value of buf) {
  console.log(value);
}
// Prints:
//   98
//   117
//   102
//   102
//   101
//   114

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.from('buffer');

for (const value of buf.values()) {
  console.log(value);
}
// Prints:
//   98
//   117
//   102
//   102
//   101
//   114

for (const value of buf) {
  console.log(value);
}
// Prints:
//   98
//   117
//   102
//   102
//   101
//   114

`buf.write(string[, offset[, length]][, encoding])`

Added in: v0.1.90

History

Version	Changes
v25.5.0, v24.13.1	supports Uint8Array as `this` value.

string <string> String to write to buf.
offset <integer> Number of bytes to skip before starting to write string. Default: 0.
length <integer> Maximum number of bytes to write (written bytes will not exceed buf.length - offset). Default: buf.length - offset.
encoding <string> The character encoding of string. Default: 'utf8'.
Returns: <integer> Number of bytes written.

Writes string to buf at offset according to the character encoding in encoding. The length parameter is the number of bytes to write. If buf did not contain enough space to fit the entire string, only part of string will be written. However, partially encoded characters will not be written.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.alloc(256);

const len = buf.write('\u00bd + \u00bc = \u00be', 0);

console.log(`${len} bytes: ${buf.toString('utf8', 0, len)}`);
// Prints: 12 bytes: ½ + ¼ = ¾

const buffer = Buffer.alloc(10);

const length = buffer.write('abcd', 8);

console.log(`${length} bytes: ${buffer.toString('utf8', 8, 10)}`);
// Prints: 2 bytes : ab

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.alloc(256);

const len = buf.write('\u00bd + \u00bc = \u00be', 0);

console.log(`${len} bytes: ${buf.toString('utf8', 0, len)}`);
// Prints: 12 bytes: ½ + ¼ = ¾

const buffer = Buffer.alloc(10);

const length = buffer.write('abcd', 8);

console.log(`${length} bytes: ${buffer.toString('utf8', 8, 10)}`);
// Prints: 2 bytes : ab

`buf.writeBigInt64BE(value[, offset])`

Added in: v12.0.0, v10.20.0

value <bigint> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy: 0 <= offset <= buf.length - 8. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset as big-endian.

value is interpreted and written as a two's complement signed integer.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(8);

buf.writeBigInt64BE(0x0102030405060708n, 0);

console.log(buf);
// Prints: <Buffer 01 02 03 04 05 06 07 08>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(8);

buf.writeBigInt64BE(0x0102030405060708n, 0);

console.log(buf);
// Prints: <Buffer 01 02 03 04 05 06 07 08>

`buf.writeBigInt64LE(value[, offset])`

Added in: v12.0.0, v10.20.0

value <bigint> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy: 0 <= offset <= buf.length - 8. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset as little-endian.

value is interpreted and written as a two's complement signed integer.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(8);

buf.writeBigInt64LE(0x0102030405060708n, 0);

console.log(buf);
// Prints: <Buffer 08 07 06 05 04 03 02 01>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(8);

buf.writeBigInt64LE(0x0102030405060708n, 0);

console.log(buf);
// Prints: <Buffer 08 07 06 05 04 03 02 01>

`buf.writeBigUInt64BE(value[, offset])`

Added in: v12.0.0, v10.20.0

History

Version	Changes
v14.10.0, v12.19.0	This function is also available as `buf.writeBigUint64BE()`.

value <bigint> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy: 0 <= offset <= buf.length - 8. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset as big-endian.

This function is also available under the writeBigUint64BE alias.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(8);

buf.writeBigUInt64BE(0xdecafafecacefaden, 0);

console.log(buf);
// Prints: <Buffer de ca fa fe ca ce fa de>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(8);

buf.writeBigUInt64BE(0xdecafafecacefaden, 0);

console.log(buf);
// Prints: <Buffer de ca fa fe ca ce fa de>

`buf.writeBigUInt64LE(value[, offset])`

Added in: v12.0.0, v10.20.0

History

Version	Changes
v14.10.0, v12.19.0	This function is also available as `buf.writeBigUint64LE()`.

value <bigint> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy: 0 <= offset <= buf.length - 8. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset as little-endian

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(8);

buf.writeBigUInt64LE(0xdecafafecacefaden, 0);

console.log(buf);
// Prints: <Buffer de fa ce ca fe fa ca de>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(8);

buf.writeBigUInt64LE(0xdecafafecacefaden, 0);

console.log(buf);
// Prints: <Buffer de fa ce ca fe fa ca de>

This function is also available under the writeBigUint64LE alias.

`buf.writeDoubleBE(value[, offset])`

Added in: v0.11.15

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

value <number> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 8. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset as big-endian. The value must be a JavaScript number. Behavior is undefined when value is anything other than a JavaScript number.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(8);

buf.writeDoubleBE(123.456, 0);

console.log(buf);
// Prints: <Buffer 40 5e dd 2f 1a 9f be 77>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(8);

buf.writeDoubleBE(123.456, 0);

console.log(buf);
// Prints: <Buffer 40 5e dd 2f 1a 9f be 77>

`buf.writeDoubleLE(value[, offset])`

Added in: v0.11.15

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

value <number> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 8. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset as little-endian. The value must be a JavaScript number. Behavior is undefined when value is anything other than a JavaScript number.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(8);

buf.writeDoubleLE(123.456, 0);

console.log(buf);
// Prints: <Buffer 77 be 9f 1a 2f dd 5e 40>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(8);

buf.writeDoubleLE(123.456, 0);

console.log(buf);
// Prints: <Buffer 77 be 9f 1a 2f dd 5e 40>

`buf.writeFloatBE(value[, offset])`

Added in: v0.11.15

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

value <number> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset as big-endian. Behavior is undefined when value is anything other than a JavaScript number.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeFloatBE(0xcafebabe, 0);

console.log(buf);
// Prints: <Buffer 4f 4a fe bb>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(4);

buf.writeFloatBE(0xcafebabe, 0);

console.log(buf);
// Prints: <Buffer 4f 4a fe bb>

`buf.writeFloatLE(value[, offset])`

Added in: v0.11.15

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

value <number> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset as little-endian. Behavior is undefined when value is anything other than a JavaScript number.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeFloatLE(0xcafebabe, 0);

console.log(buf);
// Prints: <Buffer bb fe 4a 4f>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(4);

buf.writeFloatLE(0xcafebabe, 0);

console.log(buf);
// Prints: <Buffer bb fe 4a 4f>

`buf.writeInt8(value[, offset])`

Added in: v0.5.0

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

value <integer> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 1. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset. value must be a valid signed 8-bit integer. Behavior is undefined when value is anything other than a signed 8-bit integer.

value is interpreted and written as a two's complement signed integer.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(2);

buf.writeInt8(2, 0);
buf.writeInt8(-2, 1);

console.log(buf);
// Prints: <Buffer 02 fe>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(2);

buf.writeInt8(2, 0);
buf.writeInt8(-2, 1);

console.log(buf);
// Prints: <Buffer 02 fe>

`buf.writeInt16BE(value[, offset])`

Added in: v0.5.5

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

value <integer> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 2. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset as big-endian. The value must be a valid signed 16-bit integer. Behavior is undefined when value is anything other than a signed 16-bit integer.

The value is interpreted and written as a two's complement signed integer.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(2);

buf.writeInt16BE(0x0102, 0);

console.log(buf);
// Prints: <Buffer 01 02>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(2);

buf.writeInt16BE(0x0102, 0);

console.log(buf);
// Prints: <Buffer 01 02>

`buf.writeInt16LE(value[, offset])`

Added in: v0.5.5

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

value <integer> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 2. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset as little-endian. The value must be a valid signed 16-bit integer. Behavior is undefined when value is anything other than a signed 16-bit integer.

The value is interpreted and written as a two's complement signed integer.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(2);

buf.writeInt16LE(0x0304, 0);

console.log(buf);
// Prints: <Buffer 04 03>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(2);

buf.writeInt16LE(0x0304, 0);

console.log(buf);
// Prints: <Buffer 04 03>

`buf.writeInt32BE(value[, offset])`

Added in: v0.5.5

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

value <integer> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset as big-endian. The value must be a valid signed 32-bit integer. Behavior is undefined when value is anything other than a signed 32-bit integer.

The value is interpreted and written as a two's complement signed integer.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeInt32BE(0x01020304, 0);

console.log(buf);
// Prints: <Buffer 01 02 03 04>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(4);

buf.writeInt32BE(0x01020304, 0);

console.log(buf);
// Prints: <Buffer 01 02 03 04>

`buf.writeInt32LE(value[, offset])`

Added in: v0.5.5

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

value <integer> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset as little-endian. The value must be a valid signed 32-bit integer. Behavior is undefined when value is anything other than a signed 32-bit integer.

The value is interpreted and written as a two's complement signed integer.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeInt32LE(0x05060708, 0);

console.log(buf);
// Prints: <Buffer 08 07 06 05>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(4);

buf.writeInt32LE(0x05060708, 0);

console.log(buf);
// Prints: <Buffer 08 07 06 05>

`buf.writeIntBE(value, offset, byteLength)`

Added in: v0.11.15

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset and `byteLength` to `uint32` anymore.

value <integer> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - byteLength.
byteLength <integer> Number of bytes to write. Must satisfy 0 < byteLength <= 6.
Returns: <integer> offset plus the number of bytes written.

Writes byteLength bytes of value to buf at the specified offset as big-endian. Supports up to 48 bits of accuracy. Behavior is undefined when value is anything other than a signed integer.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(6);

buf.writeIntBE(0x1234567890ab, 0, 6);

console.log(buf);
// Prints: <Buffer 12 34 56 78 90 ab>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(6);

buf.writeIntBE(0x1234567890ab, 0, 6);

console.log(buf);
// Prints: <Buffer 12 34 56 78 90 ab>

`buf.writeIntLE(value, offset, byteLength)`

Added in: v0.11.15

History

Version	Changes
v10.0.0	Removed `noAssert` and no implicit coercion of the offset and `byteLength` to `uint32` anymore.

value <integer> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - byteLength.
byteLength <integer> Number of bytes to write. Must satisfy 0 < byteLength <= 6.
Returns: <integer> offset plus the number of bytes written.

Writes byteLength bytes of value to buf at the specified offset as little-endian. Supports up to 48 bits of accuracy. Behavior is undefined when value is anything other than a signed integer.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(6);

buf.writeIntLE(0x1234567890ab, 0, 6);

console.log(buf);
// Prints: <Buffer ab 90 78 56 34 12>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(6);

buf.writeIntLE(0x1234567890ab, 0, 6);

console.log(buf);
// Prints: <Buffer ab 90 78 56 34 12>

`buf.writeUInt8(value[, offset])`

Added in: v0.5.0

History

Version	Changes
v14.9.0, v12.19.0	This function is also available as `buf.writeUint8()`.
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

value <integer> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 1. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset. value must be a valid unsigned 8-bit integer. Behavior is undefined when value is anything other than an unsigned 8-bit integer.

This function is also available under the writeUint8 alias.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeUInt8(0x3, 0);
buf.writeUInt8(0x4, 1);
buf.writeUInt8(0x23, 2);
buf.writeUInt8(0x42, 3);

console.log(buf);
// Prints: <Buffer 03 04 23 42>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(4);

buf.writeUInt8(0x3, 0);
buf.writeUInt8(0x4, 1);
buf.writeUInt8(0x23, 2);
buf.writeUInt8(0x42, 3);

console.log(buf);
// Prints: <Buffer 03 04 23 42>

`buf.writeUInt16BE(value[, offset])`

Added in: v0.5.5

History

Version	Changes
v14.9.0, v12.19.0	This function is also available as `buf.writeUint16BE()`.
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

value <integer> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 2. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset as big-endian. The value must be a valid unsigned 16-bit integer. Behavior is undefined when value is anything other than an unsigned 16-bit integer.

This function is also available under the writeUint16BE alias.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeUInt16BE(0xdead, 0);
buf.writeUInt16BE(0xbeef, 2);

console.log(buf);
// Prints: <Buffer de ad be ef>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(4);

buf.writeUInt16BE(0xdead, 0);
buf.writeUInt16BE(0xbeef, 2);

console.log(buf);
// Prints: <Buffer de ad be ef>

`buf.writeUInt16LE(value[, offset])`

Added in: v0.5.5

History

Version	Changes
v14.9.0, v12.19.0	This function is also available as `buf.writeUint16LE()`.
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

value <integer> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 2. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset as little-endian. The value must be a valid unsigned 16-bit integer. Behavior is undefined when value is anything other than an unsigned 16-bit integer.

This function is also available under the writeUint16LE alias.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeUInt16LE(0xdead, 0);
buf.writeUInt16LE(0xbeef, 2);

console.log(buf);
// Prints: <Buffer ad de ef be>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(4);

buf.writeUInt16LE(0xdead, 0);
buf.writeUInt16LE(0xbeef, 2);

console.log(buf);
// Prints: <Buffer ad de ef be>

`buf.writeUInt32BE(value[, offset])`

Added in: v0.5.5

History

Version	Changes
v14.9.0, v12.19.0	This function is also available as `buf.writeUint32BE()`.
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

value <integer> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset as big-endian. The value must be a valid unsigned 32-bit integer. Behavior is undefined when value is anything other than an unsigned 32-bit integer.

This function is also available under the writeUint32BE alias.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeUInt32BE(0xfeedface, 0);

console.log(buf);
// Prints: <Buffer fe ed fa ce>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(4);

buf.writeUInt32BE(0xfeedface, 0);

console.log(buf);
// Prints: <Buffer fe ed fa ce>

`buf.writeUInt32LE(value[, offset])`

Added in: v0.5.5

History

Version	Changes
v14.9.0, v12.19.0	This function is also available as `buf.writeUint32LE()`.
v10.0.0	Removed `noAssert` and no implicit coercion of the offset to `uint32` anymore.

value <integer> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - 4. Default: 0.
Returns: <integer> offset plus the number of bytes written.

Writes value to buf at the specified offset as little-endian. The value must be a valid unsigned 32-bit integer. Behavior is undefined when value is anything other than an unsigned 32-bit integer.

This function is also available under the writeUint32LE alias.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(4);

buf.writeUInt32LE(0xfeedface, 0);

console.log(buf);
// Prints: <Buffer ce fa ed fe>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(4);

buf.writeUInt32LE(0xfeedface, 0);

console.log(buf);
// Prints: <Buffer ce fa ed fe>

`buf.writeUIntBE(value, offset, byteLength)`

Added in: v0.5.5

History

Version	Changes
v14.9.0, v12.19.0	This function is also available as `buf.writeUintBE()`.
v10.0.0	Removed `noAssert` and no implicit coercion of the offset and `byteLength` to `uint32` anymore.

value <integer> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - byteLength.
byteLength <integer> Number of bytes to write. Must satisfy 0 < byteLength <= 6.
Returns: <integer> offset plus the number of bytes written.

Writes byteLength bytes of value to buf at the specified offset as big-endian. Supports up to 48 bits of accuracy. Behavior is undefined when value is anything other than an unsigned integer.

This function is also available under the writeUintBE alias.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(6);

buf.writeUIntBE(0x1234567890ab, 0, 6);

console.log(buf);
// Prints: <Buffer 12 34 56 78 90 ab>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(6);

buf.writeUIntBE(0x1234567890ab, 0, 6);

console.log(buf);
// Prints: <Buffer 12 34 56 78 90 ab>

`buf.writeUIntLE(value, offset, byteLength)`

Added in: v0.5.5

History

Version	Changes
v14.9.0, v12.19.0	This function is also available as `buf.writeUintLE()`.
v10.0.0	Removed `noAssert` and no implicit coercion of the offset and `byteLength` to `uint32` anymore.

value <integer> Number to be written to buf.
offset <integer> Number of bytes to skip before starting to write. Must satisfy 0 <= offset <= buf.length - byteLength.
byteLength <integer> Number of bytes to write. Must satisfy 0 < byteLength <= 6.
Returns: <integer> offset plus the number of bytes written.

This function is also available under the writeUintLE alias.

JavaScript modules

import { Buffer } from 'node:buffer';

const buf = Buffer.allocUnsafe(6);

buf.writeUIntLE(0x1234567890ab, 0, 6);

console.log(buf);
// Prints: <Buffer ab 90 78 56 34 12>

CommonJS

const { Buffer } = require('node:buffer');

const buf = Buffer.allocUnsafe(6);

buf.writeUIntLE(0x1234567890ab, 0, 6);

console.log(buf);
// Prints: <Buffer ab 90 78 56 34 12>

`new Buffer(array)`

Deprecated in: v6.0.0

History

Version	Changes
v10.0.0	Calling this constructor emits a deprecation warning when run from code outside the `node_modules` directory.
v7.2.1	Calling this constructor no longer emits a deprecation warning.
v7.0.0	Calling this constructor emits a deprecation warning now.

Stability: 0 - Deprecated: Use Buffer.from(array) instead.

array <integer[]> An array of bytes to copy from.

See Buffer.from(array).

`new Buffer(arrayBuffer[, byteOffset[, length]])`

Added in: v3.0.0Deprecated in: v6.0.0

History

Version	Changes
v10.0.0	Calling this constructor emits a deprecation warning when run from code outside the `node_modules` directory.
v7.2.1	Calling this constructor no longer emits a deprecation warning.
v7.0.0	Calling this constructor emits a deprecation warning now.
v6.0.0	The `byteOffset` and `length` parameters are supported now.

Stability: 0 - Deprecated: Use Buffer.from(arrayBuffer[, byteOffset[, length]]) instead.

arrayBuffer <ArrayBuffer> | <SharedArrayBuffer> An <ArrayBuffer>, <SharedArrayBuffer> or the .buffer property of a <TypedArray>.
byteOffset <integer> Index of first byte to expose. Default: 0.
length <integer> Number of bytes to expose. Default: arrayBuffer.byteLength - byteOffset.

See Buffer.from(arrayBuffer[, byteOffset[, length]]).

`new Buffer(buffer)`

Deprecated in: v6.0.0

History

Version	Changes
v10.0.0	Calling this constructor emits a deprecation warning when run from code outside the `node_modules` directory.
v7.2.1	Calling this constructor no longer emits a deprecation warning.
v7.0.0	Calling this constructor emits a deprecation warning now.

Stability: 0 - Deprecated: Use Buffer.from(buffer) instead.

buffer <Buffer> | <Uint8Array> An existing Buffer or <Uint8Array> from which to copy data.

See Buffer.from(buffer).

`new Buffer(size)`

Deprecated in: v6.0.0

History

Version	Changes
v10.0.0	Calling this constructor emits a deprecation warning when run from code outside the `node_modules` directory.
v8.0.0	The `new Buffer(size)` will return zero-filled memory by default.
v7.2.1	Calling this constructor no longer emits a deprecation warning.
v7.0.0	Calling this constructor emits a deprecation warning now.

Stability: 0 - Deprecated: Use Buffer.alloc() instead (also see Buffer.allocUnsafe()).

size <integer> The desired length of the new Buffer.

See Buffer.alloc() and Buffer.allocUnsafe(). This variant of the constructor is equivalent to Buffer.alloc().

`new Buffer(string[, encoding])`

Deprecated in: v6.0.0

History

Version	Changes
v10.0.0	Calling this constructor emits a deprecation warning when run from code outside the `node_modules` directory.
v7.2.1	Calling this constructor no longer emits a deprecation warning.
v7.0.0	Calling this constructor emits a deprecation warning now.

Stability: 0 - Deprecated: Use Buffer.from(string[, encoding]) instead.

string <string> String to encode.
encoding <string> The encoding of string. Default: 'utf8'.

See Buffer.from(string[, encoding]).

Class: `File`

Added in: v19.2.0, v18.13.0

History

Version	Changes
v23.0.0	Makes File instances cloneable.
v20.0.0	No longer experimental.

Extends: <Blob>

A <File> provides information about files.

`new buffer.File(sources, fileName[, options])`

Added in: v19.2.0, v18.13.0

sources <string[]> | <ArrayBuffer[]> | <TypedArray[]> | <DataView[]> | <Blob[]> | <File[]> An array of string, <ArrayBuffer>, <TypedArray>, <DataView>, <File>, or <Blob> objects, or any mix of such objects, that will be stored within the File.
fileName <string> The name of the file.
options <Object>
- endings <string> One of either 'transparent' or 'native'. When set to 'native', line endings in string source parts will be converted to the platform native line-ending as specified by require('node:os').EOL.
- type <string> The File content-type.
- lastModified <number> The last modified date of the file. Default: Date.now().

`file.name`

Added in: v19.2.0, v18.13.0

Type: <string>

The name of the File.

`file.lastModified`

Added in: v19.2.0, v18.13.0

Type: <number>

The last modified date of the File.

`node:buffer` module APIs

While, the Buffer object is available as a global, there are additional Buffer-related APIs that are available only via the node:buffer module accessed using require('node:buffer').

`buffer.atob(data)`

Added in: v15.13.0, v14.17.0

Stability: 3 - Legacy. Use Buffer.from(data, 'base64') instead.

data <any> The Base64-encoded input string.

Decodes a string of Base64-encoded data into bytes, and encodes those bytes into a string using Latin-1 (ISO-8859-1).

The data may be any JavaScript-value that can be coerced into a string.

This function is only provided for compatibility with legacy web platform APIs and should never be used in new code, because they use strings to represent binary data and predate the introduction of typed arrays in JavaScript. For code running using Node.js APIs, converting between base64-encoded strings and binary data should be performed using Buffer.from(str, 'base64') and buf.toString('base64').

An automated migration is available (source:

npx codemod@latest @nodejs/buffer-atob-btoa
bashcopy

`buffer.btoa(data)`

Added in: v15.13.0, v14.17.0

Stability: 3 - Legacy. Use buf.toString('base64') instead.

data <any> An ASCII (Latin1) string.

Decodes a string into bytes using Latin-1 (ISO-8859), and encodes those bytes into a string using Base64.

The data may be any JavaScript-value that can be coerced into a string.

An automated migration is available (source:

npx codemod@latest @nodejs/buffer-atob-btoa
bashcopy

`buffer.isAscii(input)`

Added in: v19.6.0, v18.15.0

input <Buffer> | <ArrayBuffer> | <TypedArray> The input to validate.
Returns: <boolean>

This function returns true if input contains only valid ASCII-encoded data, including the case in which input is empty.

Throws if the input is a detached array buffer.

`buffer.isUtf8(input)`

Added in: v19.4.0, v18.14.0

input <Buffer> | <ArrayBuffer> | <TypedArray> The input to validate.
Returns: <boolean>

This function returns true if input contains only valid UTF-8-encoded data, including the case in which input is empty.

Throws if the input is a detached array buffer.

`buffer.INSPECT_MAX_BYTES`

Added in: v0.5.4

Type: <integer> Default: 50

Returns the maximum number of bytes that will be returned when buf.inspect() is called. This can be overridden by user modules. See util.inspect() for more details on buf.inspect() behavior.

`buffer.kMaxLength`

Added in: v3.0.0

Type: <integer> The largest size allowed for a single Buffer instance.

An alias for buffer.constants.MAX_LENGTH.

`buffer.kStringMaxLength`

Added in: v3.0.0

Type: <integer> The largest length allowed for a single string instance.

An alias for buffer.constants.MAX_STRING_LENGTH.

`buffer.resolveObjectURL(id)`

Added in: v16.7.0

History

Version	Changes
v24.0.0, v22.17.0	Marking the API stable.

id <string> A 'blob:nodedata:... URL string returned by a prior call to URL.createObjectURL().
Returns: <Blob>

Resolves a 'blob:nodedata:...' an associated <Blob> object registered using a prior call to URL.createObjectURL().

`buffer.transcode(source, fromEnc, toEnc)`

Added in: v7.1.0

History

Version	Changes
v8.0.0	The `source` parameter can now be a `Uint8Array`.

source <Buffer> | <Uint8Array> A Buffer or Uint8Array instance.
fromEnc <string> The current encoding.
toEnc <string> To target encoding.
Returns: <Buffer>

Re-encodes the given Buffer or Uint8Array instance from one character encoding to another. Returns a new Buffer instance.

Throws if the fromEnc or toEnc specify invalid character encodings or if conversion from fromEnc to toEnc is not permitted.

Encodings supported by buffer.transcode() are: 'ascii', 'utf8', 'utf16le', 'ucs2', 'latin1', and 'binary'.

The transcoding process will use substitution characters if a given byte sequence cannot be adequately represented in the target encoding. For instance:

JavaScript modules

import { Buffer, transcode } from 'node:buffer';

const newBuf = transcode(Buffer.from('€'), 'utf8', 'ascii');
console.log(newBuf.toString('ascii'));
// Prints: '?'

CommonJS

const { Buffer, transcode } = require('node:buffer');

const newBuf = transcode(Buffer.from('€'), 'utf8', 'ascii');
console.log(newBuf.toString('ascii'));
// Prints: '?'

Because the Euro (€) sign is not representable in US-ASCII, it is replaced with ? in the transcoded Buffer.

Buffer constants

Added in: v8.2.0

`buffer.constants.MAX_LENGTH`

Added in: v8.2.0

History

Version	Changes
v22.0.0	Value is changed to 2⁵³ - 1 on 64-bit architectures, and 2³¹ - 1 on 32-bit architectures.
v15.0.0	Value is changed to 2³² on 64-bit architectures.
v14.0.0	Value is changed from 2³¹ - 1 to 2³² - 1 on 64-bit architectures.

Type: <integer> The largest size allowed for a single Buffer instance.

On 32-bit architectures, this value is equal to 2³¹ - 1 (about 2 GiB).

On 64-bit architectures, this value is equal to Number.MAX_SAFE_INTEGER (2⁵³ - 1, about 8 PiB).

It reflects v8::Uint8Array::kMaxLength under the hood.

This value is also available as buffer.kMaxLength.

`buffer.constants.MAX_STRING_LENGTH`

Added in: v8.2.0

Type: <integer> The largest length allowed for a single string instance.

Represents the largest length that a string primitive can have, counted in UTF-16 code units.

This value may depend on the JS engine that is being used.

`Buffer.from()`, `Buffer.alloc()`, and `Buffer.allocUnsafe()`

In versions of Node.js prior to 6.0.0, Buffer instances were created using the Buffer constructor function, which allocates the returned Buffer differently based on what arguments are provided:

Passing a number as the first argument to Buffer() (e.g. new Buffer(10)) allocates a new Buffer object of the specified size. Prior to Node.js 8.0.0, the memory allocated for such Buffer instances is not initialized and can contain sensitive data. Such Buffer instances must be subsequently initialized by using either buf.fill(0) or by writing to the entire Buffer before reading data from the Buffer. While this behavior is intentional to improve performance, development experience has demonstrated that a more explicit distinction is required between creating a fast-but-uninitialized Buffer versus creating a slower-but-safer Buffer. Since Node.js 8.0.0, Buffer(num) and new Buffer(num) return a Buffer with initialized memory.
Passing a string, array, or Buffer as the first argument copies the passed object's data into the Buffer.
Passing an <ArrayBuffer> or a <SharedArrayBuffer> returns a Buffer that shares allocated memory with the given array buffer.

Because the behavior of new Buffer() is different depending on the type of the first argument, security and reliability issues can be inadvertently introduced into applications when argument validation or Buffer initialization is not performed.

For example, if an attacker can cause an application to receive a number where a string is expected, the application may call new Buffer(100) instead of new Buffer("100"), leading it to allocate a 100 byte buffer instead of allocating a 3 byte buffer with content "100". This is commonly possible using JSON API calls. Since JSON distinguishes between numeric and string types, it allows injection of numbers where a naively written application that does not validate its input sufficiently might expect to always receive a string. Before Node.js 8.0.0, the 100 byte buffer might contain arbitrary pre-existing in-memory data, so may be used to expose in-memory secrets to a remote attacker. Since Node.js 8.0.0, exposure of memory cannot occur because the data is zero-filled. However, other attacks are still possible, such as causing very large buffers to be allocated by the server, leading to performance degradation or crashing on memory exhaustion.

To make the creation of Buffer instances more reliable and less error-prone, the various forms of the new Buffer() constructor have been deprecated and replaced by separate Buffer.from(), Buffer.alloc(), and Buffer.allocUnsafe() methods.

Developers should migrate all existing uses of the new Buffer() constructors to one of these new APIs.

Buffer.from(array) returns a new Buffer that contains a copy of the provided octets.
Buffer.from(arrayBuffer[, byteOffset[, length]]) returns a new Buffer that shares the same allocated memory as the given <ArrayBuffer>.
Buffer.from(buffer) returns a new Buffer that contains a copy of the contents of the given Buffer.
Buffer.from(string[, encoding]) returns a new Buffer that contains a copy of the provided string.
Buffer.alloc(size[, fill[, encoding]]) returns a new initialized Buffer of the specified size. This method is slower than Buffer.allocUnsafe(size) but guarantees that newly created Buffer instances never contain old data that is potentially sensitive. A TypeError will be thrown if size is not a number.
Buffer.allocUnsafe(size) and Buffer.allocUnsafeSlow(size) each return a new uninitialized Buffer of the specified size. Because the Buffer is uninitialized, the allocated segment of memory might contain old data that is potentially sensitive.

Buffer instances returned by Buffer.allocUnsafe(), Buffer.from(string), Buffer.concat() and Buffer.from(array) may be allocated off a shared internal memory pool if size is less than or equal to half Buffer.poolSize. Instances returned by Buffer.allocUnsafeSlow() never use the shared internal memory pool.

The `--zero-fill-buffers` command-line option

Added in: v5.10.0

Node.js can be started using the --zero-fill-buffers command-line option to cause all newly-allocated Buffer instances to be zero-filled upon creation by default. Without the option, buffers created with Buffer.allocUnsafe() and Buffer.allocUnsafeSlow() are not zero-filled. Use of this flag can have a measurable negative impact on performance. Use the --zero-fill-buffers option only when necessary to enforce that newly allocated Buffer instances cannot contain old data that is potentially sensitive.

$ node --zero-fill-buffers
> Buffer.allocUnsafe(5);
<Buffer 00 00 00 00 00>
consolecopy

What makes `Buffer.allocUnsafe()` and `Buffer.allocUnsafeSlow()` "unsafe"?

When calling Buffer.allocUnsafe() and Buffer.allocUnsafeSlow(), the segment of allocated memory is uninitialized (it is not zeroed-out). While this design makes the allocation of memory quite fast, the allocated segment of memory might contain old data that is potentially sensitive. Using a Buffer created by Buffer.allocUnsafe() without completely overwriting the memory can allow this old data to be leaked when the Buffer memory is read.

While there are clear performance advantages to using Buffer.allocUnsafe(), extra care must be taken in order to avoid introducing security vulnerabilities into an application.

© Joyent, Inc. and other Node contributors
Licensed under the MIT License.
Node.js is a trademark of Joyent, Inc. and is used with its permission.
We are not endorsed by or affiliated with Joyent.
https://nodejs.org/api/buffer.html

Buffer

Buffers and character encodings

Buffers and TypedArrays

Buffer methods are callable with Uint8Array instances

Buffers and iteration

Class: Blob

new buffer.Blob([sources[, options]])

blob.arrayBuffer()

blob.bytes()

blob.size

blob.slice([start[, end[, type]]])

blob.stream()

blob.text()

blob.type

Blob objects and MessageChannel

Class: Buffer

Static method: Buffer.alloc(size[, fill[, encoding]])

Static method: Buffer.allocUnsafe(size)

Static method: Buffer.allocUnsafeSlow(size)

Static method: Buffer.byteLength(string[, encoding])

Static method: Buffer.compare(buf1, buf2)

Static method: Buffer.concat(list[, totalLength])

Static method: Buffer.copyBytesFrom(view[, offset[, length]])

Static method: Buffer.from(array)

Static method: Buffer.from(arrayBuffer[, byteOffset[, length]])

Static method: Buffer.from(buffer)

Static method: Buffer.from(object[, offsetOrEncoding[, length]])

Static method: Buffer.from(string[, encoding])

Static method: Buffer.isBuffer(obj)

Static method: Buffer.isEncoding(encoding)

Buffer.poolSize

buf[index]

buf.buffer

buf.byteOffset

buf.compare(target[, targetStart[, targetEnd[, sourceStart[, sourceEnd]]]])

buf.copy(target[, targetStart[, sourceStart[, sourceEnd]]])

buf.entries()

buf.equals(otherBuffer)

buf.fill(value[, offset[, end]][, encoding])

buf.includes(value[, start[, end]][, encoding])

buf.indexOf(value[, start[, end]][, encoding])

buf.keys()

buf.lastIndexOf(value[, start[, end]][, encoding])

buf.length

buf.parent

buf.readBigInt64BE([offset])

buf.readBigInt64LE([offset])

buf.readBigUInt64BE([offset])

buf.readBigUInt64LE([offset])

buf.readDoubleBE([offset])

buf.readDoubleLE([offset])

buf.readFloatBE([offset])

buf.readFloatLE([offset])

buf.readInt8([offset])

buf.readInt16BE([offset])

buf.readInt16LE([offset])

buf.readInt32BE([offset])

buf.readInt32LE([offset])

buf.readIntBE(offset, byteLength)

buf.readIntLE(offset, byteLength)

buf.readUInt8([offset])

buf.readUInt16BE([offset])

buf.readUInt16LE([offset])

buf.readUInt32BE([offset])

buf.readUInt32LE([offset])

buf.readUIntBE(offset, byteLength)

buf.readUIntLE(offset, byteLength)

buf.subarray([start[, end]])

buf.slice([start[, end]])

buf.swap16()

buf.swap32()

buf.swap64()

buf.toJSON()

buf.toString([encoding[, start[, end]]])

buf.values()

buf.write(string[, offset[, length]][, encoding])

buf.writeBigInt64BE(value[, offset])

buf.writeBigInt64LE(value[, offset])

buf.writeBigUInt64BE(value[, offset])

buf.writeBigUInt64LE(value[, offset])

Buffer methods are callable with `Uint8Array` instances

Class: `Blob`

`new buffer.Blob([sources[, options]])`

`blob.arrayBuffer()`

`blob.bytes()`

`blob.size`

`blob.slice([start[, end[, type]]])`

`blob.stream()`

`blob.text()`

`blob.type`

`Blob` objects and `MessageChannel`

Class: `Buffer`

Static method: `Buffer.alloc(size[, fill[, encoding]])`

Static method: `Buffer.allocUnsafe(size)`

Static method: `Buffer.allocUnsafeSlow(size)`

Static method: `Buffer.byteLength(string[, encoding])`

Static method: `Buffer.compare(buf1, buf2)`

Static method: `Buffer.concat(list[, totalLength])`

Static method: `Buffer.copyBytesFrom(view[, offset[, length]])`

Static method: `Buffer.from(array)`

Static method: `Buffer.from(arrayBuffer[, byteOffset[, length]])`

Static method: `Buffer.from(buffer)`

Static method: `Buffer.from(object[, offsetOrEncoding[, length]])`

Static method: `Buffer.from(string[, encoding])`

Static method: `Buffer.isBuffer(obj)`

Static method: `Buffer.isEncoding(encoding)`

`Buffer.poolSize`

`buf[index]`

`buf.buffer`

`buf.byteOffset`

`buf.compare(target[, targetStart[, targetEnd[, sourceStart[, sourceEnd]]]])`

`buf.copy(target[, targetStart[, sourceStart[, sourceEnd]]])`

`buf.entries()`

`buf.equals(otherBuffer)`

`buf.fill(value[, offset[, end]][, encoding])`

`buf.includes(value[, start[, end]][, encoding])`

`buf.indexOf(value[, start[, end]][, encoding])`

`buf.keys()`

`buf.lastIndexOf(value[, start[, end]][, encoding])`

`buf.length`

`buf.parent`

`buf.readBigInt64BE([offset])`

`buf.readBigInt64LE([offset])`

`buf.readBigUInt64BE([offset])`

`buf.readBigUInt64LE([offset])`

`buf.readDoubleBE([offset])`

`buf.readDoubleLE([offset])`

`buf.readFloatBE([offset])`

`buf.readFloatLE([offset])`

`buf.readInt8([offset])`

`buf.readInt16BE([offset])`

`buf.readInt16LE([offset])`

`buf.readInt32BE([offset])`

`buf.readInt32LE([offset])`

`buf.readIntBE(offset, byteLength)`

`buf.readIntLE(offset, byteLength)`

`buf.readUInt8([offset])`

`buf.readUInt16BE([offset])`

`buf.readUInt16LE([offset])`

`buf.readUInt32BE([offset])`

`buf.readUInt32LE([offset])`

`buf.readUIntBE(offset, byteLength)`

`buf.readUIntLE(offset, byteLength)`

`buf.subarray([start[, end]])`

`buf.slice([start[, end]])`

`buf.swap16()`

`buf.swap32()`

`buf.swap64()`

`buf.toJSON()`

`buf.toString([encoding[, start[, end]]])`

`buf.values()`

`buf.write(string[, offset[, length]][, encoding])`

`buf.writeBigInt64BE(value[, offset])`

`buf.writeBigInt64LE(value[, offset])`

`buf.writeBigUInt64BE(value[, offset])`

`buf.writeBigUInt64LE(value[, offset])`

`buf.writeDoubleBE(value[, offset])`

`buf.writeDoubleLE(value[, offset])`

`buf.writeFloatBE(value[, offset])`

`buf.writeFloatLE(value[, offset])`