JS WeakMap get()

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

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()