WeakMap.prototype.get() - JavaScript 编辑

get() 方法返回  WeakMap 指定的元素。

语法

wm.get(key);

参数

key

必须。 想要从 WeakMap 获取的元素的键。

返回值

返回与指定键相关联的值，如果 WeakMap 对象找不到这个键则返回 undefined。

例子

使用 get 方法 

var wm = new WeakMap();
wm.set(window, "foo");

wm.get(window); // 返回 "foo".
wm.get("baz");  // 返回 undefined.

规范

Specification	Status	Comment
ECMAScript 2015 (6th Edition, ECMA-262) WeakMap.prototype.get	Standard	Initial definition.
ECMAScript Latest Draft (ECMA-262) WeakMap.prototype.get	Draft

浏览器兼容性

We're converting our compatibility data into a machine-readable JSON format. This compatibility table still uses the old format, because we haven't yet converted the data it contains. Find out how you can help!

• Desktop
• Mobile

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

Firefox 中的注意事项

• Prior to SpiderMonkey 38 (Firefox 38 / Thunderbird 38 / SeaMonkey 2.35), this method threw a 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).

相关链接

• WeakMap
• WeakMap.set()
• WeakMap.has()