get()
方法返回 WeakMap
指定的元素。
wm.get(key);
WeakMap
获取的元素的键。WeakMap
对象找不到这个键则返回 undefined
。get
方法
var wm = new WeakMap();
wm.set(window, "foo");
wm.get(window); // 返回 "foo".
wm.get("baz"); // 返回 undefined.
Specification | Status | Comment |
---|---|---|
ECMAScript 2015 (6th Edition, ECMA-262) WeakMap.prototype.get |
Standard | Initial definition. |
ECMAScript Latest Draft (ECMA-262) WeakMap.prototype.get |
Draft |
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari |
---|---|---|---|---|---|
Basic support | 36 | 6.0 (6.0) | 11 | 23 | 7.1 |
Feature | Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|
Basic support | 未实现 | 6.0 (6.0) | 未实现 | 未实现 | 8 |
TypeError
when the key parameter was not an object. However, the latest ES6 standard specifies to return undefined
instead. Furthermore, WeakMap.prototype.get
accepted an optional second argument as a fallback value, which is not part of the standard. Both non-standard behaviors are removed in version 38 and higher (bug 1127827).