Atomics.xor()

Atomics .xor() 静态方法会在数组中给定位置进行一次按位异或操作,并返回该位置的旧值。这个原子操作保证在修改后的值被写回之前不会发生其他写操作。

语法

Atomics.xor(typedArray, index, value)

参数

typedArray
一个共享的整型 typed array。例如  Int8Array, Uint8Array, Int16Array, Uint16Array, Int32Array, 或者  Uint32Array.
index
typedArray 中需要进行按位异或的索引位置。
value
要进行按位异或的数字。

返回值

给定位置的旧值 (typedArray[index])。

异常

  • 假如 typedArray 不是允许的整型之一,则抛出 TypeError
  • 假如 typedArray 不是一个共享的整型 typed array,则抛出 TypeError
  • 如果 index 超出了 typedArray 的边界,则抛出 RangeError

描述

如果a和b不同,则按位异或操作产生1。异或操作的真值表如下:

a b a ^ b
0 0 0
0 1 1
1 0 1
1 1 0

例如,按位异或 5 & 1 将返回 0100,而 0100 是十进制为 4 。

5  0101
1  0001
   ----
4  0100

例子

const sab = new SharedArrayBuffer(1024);
const ta = new Uint8Array(sab);
ta[0] = 5;

Atomics.xor(ta, 0, 1); // returns 5, the old value
Atomics.load(ta, 0);  // 4

规范

Specification Status Comment
ECMAScript Latest Draft (ECMA-262)
Atomics.xor
Draft Initial definition in ES2017.

浏览器支持

Update compatibility data on GitHub
Desktop Mobile Server
Chrome Edge Firefox Internet Explorer Opera Safari Android webview Chrome for Android Firefox for Android Opera for Android Safari on iOS Samsung Internet Node.js
xor 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.
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
Notes
No support No
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.
nodejs Full support 8.10.0

Legend

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

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