Atomics.add() 静态方法会将给定的值加到数组里的某个特定位置上,并返回该位置的旧值。此原子操作保证在写上修改的值之前不会发生其他写操作。

语法

Atomics.add(typedArray, index, value)

参数

typedArray
一个共享的整型 typed array。例如 Int8ArrayUint8ArrayInt16ArrayUint16ArrayInt32Array,或者 Uint32Array
index
typedArray 中的位置,该位置数值会被加总并更新。
value
增加的数字。

返回值

给定位置的旧值(typedArray[index])

错误

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

示例

var sab = new SharedArrayBuffer(1024);
var ta = new Uint8Array(sab);

Atomics.add(ta, 0, 12); // returns 0, the old value
Atomics.load(ta, 0); // 12

规范

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

浏览器支持

FeatureChromeEdgeFirefoxInternet ExplorerOperaSafari
Basic support601162

573 4

55 — 57

46 — 555

No No10.1 —?
FeatureAndroid webviewChrome for AndroidEdge mobileFirefox for AndroidOpera AndroidiOS SafariSamsung Internet
Basic support601601 ?

573 4

55 — 57

46 — 555

No No No

1. 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.

2. Support was removed to mitigate speculative execution side-channel attacks (Windows blog).

3. Support was disabled by default to mitigate speculative execution side-channel attacks (Mozilla Security Blog).

4. 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.

5. 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.

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