ArrayBuffer.prototype.transferToFixedLength()

The transferToFixedLength() method of ArrayBuffer instances creates a new non-resizable ArrayBuffer with the same byte content as this buffer, then detaches this buffer.

Syntax

transferToFixedLength()
transferToFixedLength(newByteLength)

Parameters

newByteLength

The byteLength of the new ArrayBuffer. Defaults to the byteLength of this ArrayBuffer.

• If newByteLength is smaller than the byteLength of this ArrayBuffer, the "overflowing" bytes are dropped.
• If newByteLength is larger than the byteLength of this ArrayBuffer, the extra bytes are filled with zeros.

Return value

A new ArrayBuffer object. Its contents are initialized to the contents of this ArrayBuffer, and extra bytes, if any, are filled with zeros. The new ArrayBuffer is always non-resizable. The original ArrayBuffer is detached.

Exceptions

TypeError

Thrown if this ArrayBuffer is already detached, or if it can only be detached by designated operations. Currently, only certain web APIs are capable of creating ArrayBuffer objects with designated detaching methods, such as GPUBuffer.getMappedRange() and WebAssembly.Memory.buffer.

Description

Unlike transfer(), transferToFixedLength() always creates a non-resizable ArrayBuffer. This means newByteLength can be larger than the maxByteLength, even if this ArrayBuffer is resizable. See transferring ArrayBuffers for more information.

Examples

Transferring a resizable ArrayBuffer to fixed-length

const buffer = new ArrayBuffer(8, { maxByteLength: 16 });
const view = new Uint8Array(buffer);
view[1] = 2;
view[7] = 4;

const buffer2 = buffer.transferToFixedLength();
console.log(buffer2.byteLength); // 8
console.log(buffer2.resizable); // false
const view2 = new Uint8Array(buffer2);
console.log(view2[1]); // 2
console.log(view2[7]); // 4

Using transferToFixedLength, newByteLength can be larger than the maxByteLength of the original ArrayBuffer.

const buffer = new ArrayBuffer(8, { maxByteLength: 16 });
const view = new Uint8Array(buffer);
view[1] = 2;
view[7] = 4;

const buffer2 = buffer.transferToFixedLength(20);
console.log(buffer2.byteLength); // 20
console.log(buffer2.resizable); // false
const view2 = new Uint8Array(buffer2);
console.log(view2[1]); // 2
console.log(view2[7]); // 4

Specifications

Browser compatibility

See also

• Polyfill of ArrayBuffer.prototype.transferToFixedLength in core-js
• es-shims polyfill of ArrayBuffer.prototype.transferToFixedLength
• ArrayBuffer
• ArrayBuffer.prototype.detached
• ArrayBuffer.prototype.transfer()