util/types

Usage in Deno

import * as mod from "node:util/types";

function isAnyArrayBuffer

Usage in Deno

import { isAnyArrayBuffer } from "node:util/types";

isAnyArrayBuffer(object: unknown): object is ArrayBufferLike

Returns true if the value is a built-in ArrayBuffer or SharedArrayBuffer instance.

See also util.types.isArrayBuffer() and util.types.isSharedArrayBuffer().

util.types.isAnyArrayBuffer(new ArrayBuffer());  // Returns true
util.types.isAnyArrayBuffer(new SharedArrayBuffer());  // Returns true

Parameters

object: unknown

Return Type

object is ArrayBufferLike

function isArrayBuffer

Usage in Deno

import { isArrayBuffer } from "node:util/types";

isArrayBuffer(object: unknown): object is ArrayBuffer

Returns true if the value is a built-in ArrayBuffer instance. This does not include SharedArrayBuffer instances. Usually, it is desirable to test for both; See util.types.isAnyArrayBuffer() for that.

util.types.isArrayBuffer(new ArrayBuffer());  // Returns true
util.types.isArrayBuffer(new SharedArrayBuffer());  // Returns false

Parameters

object: unknown

Return Type

object is ArrayBuffer

function isArrayBufferView

Usage in Deno

import { isArrayBufferView } from "node:util/types";

isArrayBufferView(object: unknown): object is ArrayBufferView

Returns true if the value is an instance of one of the ArrayBuffer views, such as typed array objects or DataView. Equivalent to ArrayBuffer.isView().

util.types.isArrayBufferView(new Int8Array());  // true
util.types.isArrayBufferView(Buffer.from('hello world')); // true
util.types.isArrayBufferView(new DataView(new ArrayBuffer(16)));  // true
util.types.isArrayBufferView(new ArrayBuffer());  // false

Parameters

object: unknown

Return Type

object is ArrayBufferView

function isAsyncFunction

Usage in Deno

import { isAsyncFunction } from "node:util/types";

isAsyncFunction(object: unknown): boolean

Returns true if the value is an async function. This only reports back what the JavaScript engine is seeing; in particular, the return value may not match the original source code if a transpilation tool was used.

util.types.isAsyncFunction(function foo() {});  // Returns false
util.types.isAsyncFunction(async function foo() {});  // Returns true

Parameters

object: unknown

Return Type

boolean

function isBigInt64Array

Usage in Deno

import { isBigInt64Array } from "node:util/types";

isBigInt64Array(value: unknown): value is BigInt64Array

Returns true if the value is a BigInt64Array instance.

util.types.isBigInt64Array(new BigInt64Array());   // Returns true
util.types.isBigInt64Array(new BigUint64Array());  // Returns false

Parameters

value: unknown

Return Type

value is BigInt64Array

function isBigIntObject

Usage in Deno

import { isBigIntObject } from "node:util/types";

isBigIntObject(object: unknown): object is BigInt

Returns true if the value is a BigInt object, e.g. created by Object(BigInt(123)).

util.types.isBigIntObject(Object(BigInt(123)));   // Returns true
util.types.isBigIntObject(BigInt(123));   // Returns false
util.types.isBigIntObject(123);  // Returns false

Parameters

object: unknown

Return Type

object is BigInt

function isBigUint64Array

Usage in Deno

import { isBigUint64Array } from "node:util/types";

isBigUint64Array(value: unknown): value is BigUint64Array

Returns true if the value is a BigUint64Array instance.

util.types.isBigUint64Array(new BigInt64Array());   // Returns false
util.types.isBigUint64Array(new BigUint64Array());  // Returns true

Parameters

value: unknown

Return Type

value is BigUint64Array

function isBooleanObject

Usage in Deno

import { isBooleanObject } from "node:util/types";

isBooleanObject(object: unknown): object is Boolean

Returns true if the value is a boolean object, e.g. created by new Boolean().

util.types.isBooleanObject(false);  // Returns false
util.types.isBooleanObject(true);   // Returns false
util.types.isBooleanObject(new Boolean(false)); // Returns true
util.types.isBooleanObject(new Boolean(true));  // Returns true
util.types.isBooleanObject(Boolean(false)); // Returns false
util.types.isBooleanObject(Boolean(true));  // Returns false

Parameters

object: unknown

Return Type

object is Boolean

function isBoxedPrimitive

Usage in Deno

import { isBoxedPrimitive } from "node:util/types";

isBoxedPrimitive(object: unknown): object is 
String
 | Number
 | BigInt
 | Boolean
 | Symbol

Returns true if the value is any boxed primitive object, e.g. created by new Boolean(), new String() or Object(Symbol()).

For example:

util.types.isBoxedPrimitive(false); // Returns false
util.types.isBoxedPrimitive(new Boolean(false)); // Returns true
util.types.isBoxedPrimitive(Symbol('foo')); // Returns false
util.types.isBoxedPrimitive(Object(Symbol('foo'))); // Returns true
util.types.isBoxedPrimitive(Object(BigInt(5))); // Returns true

Parameters

object: unknown

Return Type

object is 
String
 | Number
 | BigInt
 | Boolean
 | Symbol

function isCryptoKey

Usage in Deno

import { isCryptoKey } from "node:util/types";

isCryptoKey(object: unknown): object is webcrypto.CryptoKey

Returns true if value is a CryptoKey, false otherwise.

Parameters

object: unknown

Return Type

object is webcrypto.CryptoKey

function isDataView

Usage in Deno

import { isDataView } from "node:util/types";

isDataView(object: unknown): object is DataView

Returns true if the value is a built-in DataView instance.

const ab = new ArrayBuffer(20);
util.types.isDataView(new DataView(ab));  // Returns true
util.types.isDataView(new Float64Array());  // Returns false

Parameters

object: unknown

Return Type

object is DataView

function isDate

Usage in Deno

import { isDate } from "node:util/types";

isDate(object: unknown): object is Date

Returns true if the value is a built-in Date instance.

util.types.isDate(new Date());  // Returns true

Parameters

object: unknown

Return Type

object is Date

function isExternal

Usage in Deno

import { isExternal } from "node:util/types";

isExternal(object: unknown): boolean

Returns true if the value is a native External value.

A native External value is a special type of object that contains a raw C++ pointer (void*) for access from native code, and has no other properties. Such objects are created either by Node.js internals or native addons. In JavaScript, they are frozen objects with anull prototype.

#include <js_native_api.h>
#include <stdlib.h>
napi_value result;
static napi_value MyNapi(napi_env env, napi_callback_info info) {
  int* raw = (int*) malloc(1024);
  napi_status status = napi_create_external(env, (void*) raw, NULL, NULL, &#x26;result);
  if (status != napi_ok) {
    napi_throw_error(env, NULL, "napi_create_external failed");
    return NULL;
  }
  return result;
}
...
DECLARE_NAPI_PROPERTY("myNapi", MyNapi)
...

const native = require('napi_addon.node');
const data = native.myNapi();
util.types.isExternal(data); // returns true
util.types.isExternal(0); // returns false
util.types.isExternal(new String('foo')); // returns false

For further information on napi_create_external, refer to napi_create_external().

Parameters

object: unknown

Return Type

boolean

function isFloat32Array

Usage in Deno

import { isFloat32Array } from "node:util/types";

isFloat32Array(object: unknown): object is Float32Array

Returns true if the value is a built-in Float32Array instance.

util.types.isFloat32Array(new ArrayBuffer());  // Returns false
util.types.isFloat32Array(new Float32Array());  // Returns true
util.types.isFloat32Array(new Float64Array());  // Returns false

Parameters

object: unknown

Return Type

object is Float32Array

function isFloat64Array

Usage in Deno

import { isFloat64Array } from "node:util/types";

isFloat64Array(object: unknown): object is Float64Array

Returns true if the value is a built-in Float64Array instance.

util.types.isFloat64Array(new ArrayBuffer());  // Returns false
util.types.isFloat64Array(new Uint8Array());  // Returns false
util.types.isFloat64Array(new Float64Array());  // Returns true

Parameters

object: unknown

Return Type

object is Float64Array

function isGeneratorFunction

Usage in Deno

import { isGeneratorFunction } from "node:util/types";

isGeneratorFunction(object: unknown): object is GeneratorFunction

Returns true if the value is a generator function. This only reports back what the JavaScript engine is seeing; in particular, the return value may not match the original source code if a transpilation tool was used.

util.types.isGeneratorFunction(function foo() {});  // Returns false
util.types.isGeneratorFunction(function* foo() {});  // Returns true

Parameters

object: unknown

Return Type

object is GeneratorFunction

function isGeneratorObject

Usage in Deno

import { isGeneratorObject } from "node:util/types";

isGeneratorObject(object: unknown): object is Generator

Returns true if the value is a generator object as returned from a built-in generator function. This only reports back what the JavaScript engine is seeing; in particular, the return value may not match the original source code if a transpilation tool was used.

function* foo() {}
const generator = foo();
util.types.isGeneratorObject(generator);  // Returns true

Parameters

object: unknown

Return Type

object is Generator

function isInt16Array

Usage in Deno

import { isInt16Array } from "node:util/types";

isInt16Array(object: unknown): object is Int16Array

Returns true if the value is a built-in Int16Array instance.

util.types.isInt16Array(new ArrayBuffer());  // Returns false
util.types.isInt16Array(new Int16Array());  // Returns true
util.types.isInt16Array(new Float64Array());  // Returns false

Parameters

object: unknown

Return Type

object is Int16Array

function isInt32Array

Usage in Deno

import { isInt32Array } from "node:util/types";

isInt32Array(object: unknown): object is Int32Array

Returns true if the value is a built-in Int32Array instance.

util.types.isInt32Array(new ArrayBuffer());  // Returns false
util.types.isInt32Array(new Int32Array());  // Returns true
util.types.isInt32Array(new Float64Array());  // Returns false

Parameters

object: unknown

Return Type

object is Int32Array

function isInt8Array

Usage in Deno

import { isInt8Array } from "node:util/types";

isInt8Array(object: unknown): object is Int8Array

Returns true if the value is a built-in Int8Array instance.

util.types.isInt8Array(new ArrayBuffer());  // Returns false
util.types.isInt8Array(new Int8Array());  // Returns true
util.types.isInt8Array(new Float64Array());  // Returns false

Parameters

object: unknown

Return Type

object is Int8Array

function isKeyObject

Usage in Deno

import { isKeyObject } from "node:util/types";

isKeyObject(object: unknown): object is KeyObject

Returns true if value is a KeyObject, false otherwise.

Parameters

object: unknown

Return Type

object is KeyObject

function isMap

Usage in Deno

import { isMap } from "node:util/types";

isMap<T>(object: T | {  }): object is T extends ReadonlyMap<any, any> ? (unknown extends T ? never : ReadonlyMap<any, any>) : Map<unknown, unknown>

Returns true if the value is a built-in Map instance.

util.types.isMap(new Map());  // Returns true

Type Parameters

T

Parameters

object: T | { }

Return Type

object is T extends ReadonlyMap<any, any> ? (unknown extends T ? never : ReadonlyMap<any, any>) : Map<unknown, unknown>

function isMapIterator

Usage in Deno

import { isMapIterator } from "node:util/types";

isMapIterator(object: unknown): boolean

Returns true if the value is an iterator returned for a built-in Map instance.

const map = new Map();
util.types.isMapIterator(map.keys());  // Returns true
util.types.isMapIterator(map.values());  // Returns true
util.types.isMapIterator(map.entries());  // Returns true
util.types.isMapIterator(map[Symbol.iterator]());  // Returns true

Parameters

object: unknown

Return Type

boolean

function isModuleNamespaceObject

Usage in Deno

import { isModuleNamespaceObject } from "node:util/types";

isModuleNamespaceObject(value: unknown): boolean

Returns true if the value is an instance of a Module Namespace Object.

import * as ns from './a.js';

util.types.isModuleNamespaceObject(ns);  // Returns true

Parameters

value: unknown

Return Type

boolean

function isNativeError

Usage in Deno

import { isNativeError } from "node:util/types";

isNativeError(object: unknown): object is Error

Returns true if the value was returned by the constructor of a built-in Error type.

console.log(util.types.isNativeError(new Error()));  // true
console.log(util.types.isNativeError(new TypeError()));  // true
console.log(util.types.isNativeError(new RangeError()));  // true

Subclasses of the native error types are also native errors:

class MyError extends Error {}
console.log(util.types.isNativeError(new MyError()));  // true

A value being instanceof a native error class is not equivalent to isNativeError() returning true for that value. isNativeError() returns true for errors which come from a different realm while instanceof Error returns false for these errors:

import vm from 'node:vm';
const context = vm.createContext({});
const myError = vm.runInContext('new Error()', context);
console.log(util.types.isNativeError(myError)); // true
console.log(myError instanceof Error); // false

Conversely, isNativeError() returns false for all objects which were not returned by the constructor of a native error. That includes values which are instanceof native errors:

const myError = { __proto__: Error.prototype };
console.log(util.types.isNativeError(myError)); // false
console.log(myError instanceof Error); // true

Parameters

object: unknown

Return Type

object is Error

function isNumberObject

Usage in Deno

import { isNumberObject } from "node:util/types";

isNumberObject(object: unknown): object is Number

Returns true if the value is a number object, e.g. created by new Number().

util.types.isNumberObject(0);  // Returns false
util.types.isNumberObject(new Number(0));   // Returns true

Parameters

object: unknown

Return Type

object is Number

function isPromise

Usage in Deno

import { isPromise } from "node:util/types";

isPromise(object: unknown): object is Promise<unknown>

Returns true if the value is a built-in Promise.

util.types.isPromise(Promise.resolve(42));  // Returns true

Parameters

object: unknown

Return Type

object is Promise<unknown>

function isProxy

Usage in Deno

import { isProxy } from "node:util/types";

isProxy(object: unknown): boolean

Returns true if the value is a Proxy instance.

const target = {};
const proxy = new Proxy(target, {});
util.types.isProxy(target);  // Returns false
util.types.isProxy(proxy);  // Returns true

Parameters

object: unknown

Return Type

boolean

function isRegExp

Usage in Deno

import { isRegExp } from "node:util/types";

isRegExp(object: unknown): object is RegExp

Returns true if the value is a regular expression object.

util.types.isRegExp(/abc/);  // Returns true
util.types.isRegExp(new RegExp('abc'));  // Returns true

Parameters

object: unknown

Return Type

object is RegExp

function isSet

Usage in Deno

import { isSet } from "node:util/types";

isSet<T>(object: T | {  }): object is T extends ReadonlySet<any> ? (unknown extends T ? never : ReadonlySet<any>) : Set<unknown>

Returns true if the value is a built-in Set instance.

util.types.isSet(new Set());  // Returns true

Type Parameters

T

Parameters

object: T | { }

Return Type

object is T extends ReadonlySet<any> ? (unknown extends T ? never : ReadonlySet<any>) : Set<unknown>

function isSetIterator

Usage in Deno

import { isSetIterator } from "node:util/types";

isSetIterator(object: unknown): boolean

Returns true if the value is an iterator returned for a built-in Set instance.

const set = new Set();
util.types.isSetIterator(set.keys());  // Returns true
util.types.isSetIterator(set.values());  // Returns true
util.types.isSetIterator(set.entries());  // Returns true
util.types.isSetIterator(set[Symbol.iterator]());  // Returns true

Parameters

object: unknown

Return Type

boolean

function isSharedArrayBuffer

Usage in Deno

import { isSharedArrayBuffer } from "node:util/types";

isSharedArrayBuffer(object: unknown): object is SharedArrayBuffer

Returns true if the value is a built-in SharedArrayBuffer instance. This does not include ArrayBuffer instances. Usually, it is desirable to test for both; See util.types.isAnyArrayBuffer() for that.

util.types.isSharedArrayBuffer(new ArrayBuffer());  // Returns false
util.types.isSharedArrayBuffer(new SharedArrayBuffer());  // Returns true

Parameters

object: unknown

Return Type

object is SharedArrayBuffer

function isStringObject

Usage in Deno

import { isStringObject } from "node:util/types";

isStringObject(object: unknown): object is String

Returns true if the value is a string object, e.g. created by new String().

util.types.isStringObject('foo');  // Returns false
util.types.isStringObject(new String('foo'));   // Returns true

Parameters

object: unknown

Return Type

object is String

function isSymbolObject

Usage in Deno

import { isSymbolObject } from "node:util/types";

isSymbolObject(object: unknown): object is Symbol

Returns true if the value is a symbol object, created by calling Object() on a Symbol primitive.

const symbol = Symbol('foo');
util.types.isSymbolObject(symbol);  // Returns false
util.types.isSymbolObject(Object(symbol));   // Returns true

Parameters

object: unknown

Return Type

object is Symbol

function isTypedArray

Usage in Deno

import { isTypedArray } from "node:util/types";

isTypedArray(object: unknown): object is TypedArray

Returns true if the value is a built-in TypedArray instance.

util.types.isTypedArray(new ArrayBuffer());  // Returns false
util.types.isTypedArray(new Uint8Array());  // Returns true
util.types.isTypedArray(new Float64Array());  // Returns true

Parameters

object: unknown

Return Type

object is TypedArray

function isUint16Array

Usage in Deno

import { isUint16Array } from "node:util/types";

isUint16Array(object: unknown): object is Uint16Array

Returns true if the value is a built-in Uint16Array instance.

util.types.isUint16Array(new ArrayBuffer());  // Returns false
util.types.isUint16Array(new Uint16Array());  // Returns true
util.types.isUint16Array(new Float64Array());  // Returns false

Parameters

object: unknown

Return Type

object is Uint16Array

function isUint32Array

Usage in Deno

import { isUint32Array } from "node:util/types";

isUint32Array(object: unknown): object is Uint32Array

Returns true if the value is a built-in Uint32Array instance.

util.types.isUint32Array(new ArrayBuffer());  // Returns false
util.types.isUint32Array(new Uint32Array());  // Returns true
util.types.isUint32Array(new Float64Array());  // Returns false

Parameters

object: unknown

Return Type

object is Uint32Array

function isUint8Array

Usage in Deno

import { isUint8Array } from "node:util/types";

isUint8Array(object: unknown): object is Uint8Array

Returns true if the value is a built-in Uint8Array instance.

util.types.isUint8Array(new ArrayBuffer());  // Returns false
util.types.isUint8Array(new Uint8Array());  // Returns true
util.types.isUint8Array(new Float64Array());  // Returns false

Parameters

object: unknown

Return Type

object is Uint8Array

function isUint8ClampedArray

Usage in Deno

import { isUint8ClampedArray } from "node:util/types";

isUint8ClampedArray(object: unknown): object is Uint8ClampedArray

Returns true if the value is a built-in Uint8ClampedArray instance.

util.types.isUint8ClampedArray(new ArrayBuffer());  // Returns false
util.types.isUint8ClampedArray(new Uint8ClampedArray());  // Returns true
util.types.isUint8ClampedArray(new Float64Array());  // Returns false

Parameters

object: unknown

Return Type

object is Uint8ClampedArray

function isWeakMap

Usage in Deno

import { isWeakMap } from "node:util/types";

isWeakMap(object: unknown): object is WeakMap<object, unknown>

Returns true if the value is a built-in WeakMap instance.

util.types.isWeakMap(new WeakMap());  // Returns true

Parameters

object: unknown

Return Type

object is WeakMap<object, unknown>

function isWeakSet

Usage in Deno

import { isWeakSet } from "node:util/types";

isWeakSet(object: unknown): object is WeakSet<object>

Returns true if the value is a built-in WeakSet instance.

util.types.isWeakSet(new WeakSet());  // Returns true

Parameters

object: unknown

Return Type

object is WeakSet<object>

function isAnyArrayBuffer

Usage in Deno

Parameters

Return Type

function isArgumentsObject

Usage in Deno

Parameters

Return Type

function isArrayBuffer

Usage in Deno

Parameters

Return Type

function isArrayBufferView

Usage in Deno

Parameters

Return Type

function isAsyncFunction

Usage in Deno

Parameters

Return Type

function isBigInt64Array

Usage in Deno

Parameters

Return Type

function isBigIntObject

Usage in Deno

Parameters

Return Type

function isBigUint64Array

Usage in Deno

Parameters

Return Type

function isBooleanObject

Usage in Deno

Parameters

Return Type

function isBoxedPrimitive

Usage in Deno

Parameters

Return Type

function isCryptoKey

Usage in Deno

Parameters

Return Type

function isDataView

Usage in Deno

Parameters

Return Type

function isDate

Usage in Deno

Parameters

Return Type

function isExternal

Usage in Deno

Parameters

Return Type

function isFloat32Array

Usage in Deno

Parameters

Return Type

function isFloat64Array

Usage in Deno

Parameters

Return Type

function isGeneratorFunction

Usage in Deno

Parameters

Return Type

function isGeneratorObject

Usage in Deno

Parameters

Return Type

function isInt16Array

Usage in Deno

Parameters

Return Type

function isInt32Array

Usage in Deno

Parameters

Return Type