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• 描述
• 构造函数
• 实例方法
• 范例
• 规范
• 浏览器兼容性
• 另请参阅
• 相关话题

WeakSet object lets you store weakly held objects in a collection.

描述

WeakSet objects are collections of objects. Just as with Set s, each object in a WeakSet may occur only once; all objects in a WeakSet 's collection are unique.

The main differences to the Set object are:

• WeakSets are collections of objects only .  They cannot contain arbitrary values of any type, as Set s can.
• WeakSet is weak, meaning references to objects in a WeakSet are held weakly . If no other references to an object stored in the WeakSet exist, those objects can be garbage collected.

  • 注意： This also means that there is no list of current objects stored in the collection. WeakSets are not enumerable.

Use case: Detecting circular references

Functions that call themselves recursively need a way of guarding against circular data structures by tracking which objects have already been processed.

WeakSet s are ideal for this purpose:

// Execute a callback on everything stored inside an object
function execRecursively(fn, subject, _refs = null){
	if(!_refs)
		_refs = new WeakSet();
	// Avoid infinite recursion
	if(_refs.has(subject))
		return;
	fn(subject);
	if("object" === typeof subject){
		_refs.add(subject);
		for(let key in subject)
			execRecursively(fn, subject[key], _refs);
	}
}
const foo = {
	foo: "Foo",
	bar: {
		bar: "Bar"
	}
};
foo.bar.baz = foo; // Circular reference!
execRecursively(obj => console.log(obj), foo);
					

Here, a WeakSet is created on the first run, and passed along with every subsequent function call (using the internal _refs parameter).

The number of objects or their traversal order is immaterial, so a WeakSet is more suitable (and performant) than a Set for tracking object references, especially if a very large number of objects is involved.

构造函数

WeakSet()

创建新的 WeakSet 对象。

实例方法

WeakSet.prototype.add( value )

追加 value 到 WeakSet 对象。

WeakSet.prototype.delete( value )

移除 value 从 WeakSet . WeakSet.prototype.has( value ) will return false afterwards.

WeakSet.prototype.has( value )

Returns a boolean asserting whether value is present in the WeakSet object or not.

范例

Using the WeakSet object

const ws = new WeakSet();
const foo = {};
const bar = {};
ws.add(foo);
ws.add(bar);
ws.has(foo);    // true
ws.has(bar);    // true
ws.delete(foo); // removes foo from the set
ws.has(foo);    // false, foo has been removed
ws.has(bar);    // true, bar is retained
					

注意， foo !== bar . While they are similar objects, they are not the same object . And so they are both added to the set.

规范

规范
ECMAScript (ECMA-262) The definition of 'WeakSet' 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
WeakSet	Chrome 36	Edge 12	Firefox 34	IE No	Opera 23	Safari 9	WebView Android 37	Chrome Android 36	Firefox Android 34	Opera Android 24	Safari iOS 9	Samsung Internet Android 3.0	nodejs 0.12
WeakSet() 构造函数	Chrome 36	Edge 12	Firefox 34	IE No	Opera 23	Safari 9	WebView Android 37	Chrome Android 36	Firefox Android 34	Opera Android 24	Safari iOS 9	Samsung Internet Android 3.0	nodejs 0.12
add	Chrome 36	Edge 12	Firefox 34	IE No	Opera 23	Safari 9	WebView Android 37	Chrome Android 36	Firefox Android 34	Opera Android 24	Safari iOS 9	Samsung Internet Android 3.0	nodejs 0.12
clear 弃用 非标	Chrome 36 — 43	Edge No	Firefox 34 — 46	IE No	Opera 25 — 30	Safari No	WebView Android 37 — 43	Chrome Android 36 — 43	Firefox Android 34 — 46	Opera Android 25 — 30	Safari iOS No	Samsung Internet Android 3.0 — 4.0	nodejs No
delete	Chrome 36	Edge 12	Firefox 34	IE No	Opera 23	Safari 9	WebView Android 37	Chrome Android 36	Firefox Android 34	Opera Android 24	Safari iOS 9	Samsung Internet Android 3.0	nodejs 0.12
has	Chrome 36	Edge 12	Firefox 34	IE No	Opera 23	Safari 9	WebView Android 37	Chrome Android 36	Firefox Android 34	Opera Android 24	Safari iOS 9	Samsung Internet Android 3.0	nodejs 0.12

图例

完整支持

完整支持

不支持

不支持

非标。预期跨浏览器支持较差。

非标。预期跨浏览器支持较差。

弃用。不要用于新网站。

弃用。不要用于新网站。

另请参阅

• Map
• Set
• WeakMap

元数据

• 最后修改： May 8, 2020

相关话题

1. 标准内置对象
2. WeakSet
3. 方法
   1. WeakSet.prototype.add()
   2. WeakSet.prototype.clear()
   3. WeakSet.prototype.delete()
   4. WeakSet.prototype.has()
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()