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• 句法
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

WeakMap() 构造函数 creates WeakMap objects which are a collections of key/value pairs in which the keys are weakly referenced. The keys must be objects and the values can be arbitrary values.

You can learn more about WeakMap s in the section WeakMap object in 键控集合 .

句法

new WeakMap([iterable])
					

参数

iterable

Iterable is an Array or other iterable object whose elements are key-value pairs (2-element Arrays). Each key-value pair will be added to the new WeakMap. null is treated as undefined.

范例

使用 WeakMap

const wm1 = new WeakMap(),
      wm2 = new WeakMap(),
      wm3 = new WeakMap();
const o1 = {},
      o2 = function() {},
      o3 = window;
wm1.set(o1, 37);
wm1.set(o2, 'azerty');
wm2.set(o1, o2); // a value can be anything, including an object or a function
wm2.set(o3, undefined);
wm2.set(wm1, wm2); // keys and values can be any objects. Even WeakMaps!
wm1.get(o2); // "azerty"
wm2.get(o2); // undefined, because there is no key for o2 on wm2
wm2.get(o3); // undefined, because that is the set value
wm1.has(o2); // true
wm2.has(o2); // false
wm2.has(o3); // true (even if the value itself is 'undefined')
wm3.set(o1, 37);
wm3.get(o1); // 37
wm1.has(o1); // true
wm1.delete(o1);
wm1.has(o1); // false
					

规范

规范
ECMAScript (ECMA-262) The definition of 'WeakMap constructor' 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
WeakMap() 构造函数	Chrome 36	Edge 12	Firefox 6	IE 11	Opera 23	Safari 8	WebView Android 37	Chrome Android 36	Firefox Android 6	Opera Android 24	Safari iOS 8	Samsung Internet Android 3.0	nodejs 0.12 0.12 0.10 Disabled Disabled From version 0.10: this feature is behind the --harmony runtime flag.
new WeakMap(iterable)	Chrome 38	Edge 12	Firefox 36	IE No	Opera 25	Safari 9	WebView Android 38	Chrome Android 38	Firefox Android 36	Opera Android 25	Safari iOS 9	Samsung Internet Android 3.0	nodejs 0.12
WeakMap() without new throws	Chrome 36	Edge 12	Firefox 42	IE 11	Opera 23	Safari 9	WebView Android 37	Chrome Android 36	Firefox Android 42	Opera Android 24	Safari iOS 9	Samsung Internet Android 3.0	nodejs 0.12
new WeakMap(null)	Chrome 36	Edge 12	Firefox 37	IE 11	Opera 23	Safari 8	WebView Android 37	Chrome Android 36	Firefox Android 37	Opera Android 24	Safari iOS 8	Samsung Internet Android 3.0	nodejs 0.12 0.12 0.10 Disabled Disabled From version 0.10: this feature is behind the --harmony runtime flag.

图例

完整支持

完整支持

不支持

不支持

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

• WeakMap in the JavaScript guide
• Hiding Implementation Details with ECMAScript 6 WeakMaps
• Map
• Set
• WeakSet

元数据

• 最后修改： Jan 30, 2020

相关话题

1. 标准内置对象
2. WeakMap
3. 方法
   1. WeakMap.prototype.clear()
   2. WeakMap.prototype.delete()
   3. WeakMap.prototype.get()
   4. WeakMap.prototype.has()
   5. WeakMap.prototype.set()
4. 继承：
5. Function
6. 特性
   1. Function.arguments
   2. Function.caller
   3. Function.displayName
   4. Function.length
   5. Function.name
7. 方法
   1. Function.prototype.apply()
   2. Function.prototype.bind()
   3. Function.prototype.call()
   4. Function.prototype.toSource()
   5. Function.prototype.toString()
8. Object
9. 特性
   1. Object.prototype.__proto__
   2. Object.prototype.constructor
10. 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()