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• 句法
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

静态 Atomics .compareExchange() method exchanges a given replacement value at a given position in the array, if a given expected value equals the old value.  It returns the old value at that position whether it was equal to the expected value or not. This atomic operation guarantees that no other write happens until the modified value is written back.

The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples project, please clone https://github.com/mdn/interactive-examples and send us a pull request.

句法

Atomics.compareExchange(typedArray, index, expectedValue, replacementValue)
					

参数

typedArray

An integer typed array. One of Int8Array , Uint8Array , Int16Array , Uint16Array , Int32Array , Uint32Array , BigInt64Array ，或 BigUint64Array .

index

The position in the typedArray to exchange a value .

expectedValue

The value to check for equality.

replacementValue

The number to exchange.

返回值

The old value at the given position ( typedArray [ index ] ).

异常

• 抛出 TypeError , if typedArray is not one of the allowed integer types.
• 抛出 RangeError , if index is out of bounds in the typedArray .

范例

Using compareExchange()

const sab = new SharedArrayBuffer(1024);
const ta = new Uint8Array(sab);
ta[0] = 7;
Atomics.compareExchange(ta, 0, 7, 12); // returns 7, the old value
Atomics.load(ta, 0); // 12
					

规范

规范
ECMAScript (ECMA-262) The definition of 'Atomics.compareExchange' in that specification.

浏览器兼容性

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. 更新 GitHub 上的兼容性数据

	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
compareExchange	Chrome 68 68 不支持 60 — 63 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 79 79 不支持 16 — 17 Support was removed to mitigate speculative execution side-channel attacks (Windows blog) .	Firefox 78 78 57 Disabled 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. 不支持 55 — 57 不支持 46 — 55 Disabled Disabled ). To change preferences in Firefox, visit	IE No	Opera No	Safari 10.1 — 11.1	WebView Android 60 — 63 不支持 60 — 63 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 60 — 63 不支持 60 — 63 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 57 Disabled 57 Disabled 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. 不支持 55 — 57 不支持 46 — 55 Disabled Disabled ). To change preferences in Firefox, visit	Opera Android No	Safari iOS 10.3 — 11.3	Samsung Internet Android No 不支持 No 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 8.10.0

图例

完整支持

完整支持

不支持

不支持

见实现注意事项。

用户必须明确启用此特征。

用户必须明确启用此特征。

另请参阅

• Atomics
• Atomics.exchange()

元数据

• 最后修改： Jul 7, 2020

相关话题

1. 标准内置对象
2. Atomics
3. 方法
   1. Atomics.add()
   2. Atomics.and()
   3. Atomics.compareExchange()
   4. Atomics.exchange()
   5. Atomics.isLockFree()
   6. Atomics.load()
   7. Atomics.notify()
   8. Atomics.or()
   9. Atomics.store()
   10. Atomics.sub()
   11. Atomics.wait()
   12. Atomics.xor()
4. 继承：
5. Object
6. 特性
   1. Object.prototype.__proto__
   2. Object.prototype.constructor
7. 方法
   1. Object.prototype.__defineGetter__()
   2. Object.prototype.__defineSetter__()
   3. Object.prototype.__lookupGetter__()
   4. Object.prototype.__lookupSetter__()
   5. Object.prototype.hasOwnProperty()
   6. Object.prototype.isPrototypeOf()
   7. Object.prototype.propertyIsEnumerable()
   8. Object.prototype.toLocaleString()
   9. Object.prototype.toSource()
   10. Object.prototype.toString()
   11. Object.prototype.valueOf()
   12. Object.setPrototypeOf()