`byteLength` 访问器属性表示以字节为单位的一个`SharedArrayBuffer`的长度。

## Syntax

    sab.byteLength

## Description

The `byteLength` property is an accessor property whose set accessor function is `undefined`, meaning that you can only read this property. The value is established when the shared array is constructed and cannot be changed.

## Examples

    var sab = new SharedArrayBuffer(1024);
    sab.byteLength; // 1024

## Specifications

Specification | Status | Comment
--- | --- | ---
ECMAScript Latest Draft (ECMA-262) SharedArrayBuffer.prototype.byteLength | Draft | Initial definition in ES2017.

## Browser compatibility

The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Update compatibility data on GitHub

| Desktop | Mobile | Server
| Chrome | Edge | Firefox | Internet Explorer | Opera | Safari | Android webview | Chrome for Android | Edge Mobile | Firefox for Android | Opera for Android | Safari on iOS | Samsung Internet | Node.js
`byteLength` | Chrome Full support 68 Full support 68 No support 60 — 63 Notes Notes Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This was a temporary removal while mitigations were put in place. | Edge No support 16 — 17 Notes No support 16 — 17 Notes Notes Support was removed to mitigate speculative execution side-channel attacks (Windows blog). | Firefox Full support 57 Notes Disabled Full support 57 Notes Disabled Notes Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled Disabled From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. | IE No support No | Opera No support No | Safari No support 10.1 — ? | WebView Android No support 60 — 63 Notes No support 60 — 63 Notes Notes Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place. | Chrome Android No support 60 — 63 Notes No support 60 — 63 Notes Notes Chrome disabled SharedArrayBuffer on January 5, 2018 to help reduce the efficacy of speculative side-channel attacks. This is intended as a temporary measure until other mitigations are in place. | Edge Mobile ? | Firefox Android Full support 57 Notes Disabled Full support 57 Notes Disabled Notes Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog). Disabled From version 57: this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. No support 55 — 57 No support 46 — 55 Disabled Disabled From version 46 until version 55 (exclusive): this feature is behind the `javascript.options.shared_memory` preference (needs to be set to `true`). To change preferences in Firefox, visit about:config. | Opera Android No support No | Safari iOS No support No | Samsung Internet Android No support No | nodejs Full support 8.10.0

### Legend

Full support
  Full support
No support
  No support
Compatibility unknown
  Compatibility unknown
See implementation notes.
  See implementation notes.
User must explicitly enable this feature.
  User must explicitly enable this feature.

## See also

- `SharedArrayBuffer`