files/en-us/web/javascript/reference/global_objects/arraybuffer/transfertofixedlength/index.md

metadata

title: ArrayBuffer.prototype.transferToFixedLength()
short-title: transferToFixedLength()
slug: Web/JavaScript/Reference/Global_Objects/ArrayBuffer/transferToFixedLength
page-type: javascript-instance-method
browser-compat: javascript.builtins.ArrayBuffer.transferToFixedLength
sidebar: jsref

The transferToFixedLength() method of {{jsxref("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 {{jsxref("ArrayBuffer/byteLength", "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 {{jsxref("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

• {{jsxref("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 {{domxref("GPUBuffer.getMappedRange()")}} and WebAssembly.Memory.buffer.

Description

Unlike {{jsxref("ArrayBuffer/transfer", "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

{{Specifications}}

Browser compatibility

{{Compat}}

See also

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