WeakMap.prototype.has()
Baseline Widely available
This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.
WeakMap
实例的 has()
返回一个布尔值,指示该 WeakMap
中是否存在具有指定键的元素。
尝试一下
const weakmap1 = new WeakMap();
const object1 = {};
const object2 = {};
weakmap1.set(object1, "foo");
console.log(weakmap1.has(object1));
// Expected output: true
console.log(weakmap1.has(object2));
// Expected output: false
语法
js
has(key)
参数
key
-
要测试是否在该
WeakMap
对象中存在的元素的键。
返回值
如果指定键的元素存在于 WeakMap
对象中,则返回 true
;否则返回 false
。如果 key
不是对象或非全局注册的符号,则始终返回 false
。
示例
使用 has 方法
js
const wm = new WeakMap();
wm.set(window, "foo");
wm.has(window); // 返回 true
wm.has("baz"); // 返回 false
规范
Specification |
---|
ECMAScript® 2025 Language Specification # sec-weakmap.prototype.has |
浏览器兼容性
Report problems with this compatibility data on GitHubdesktop | mobile | server | ||||||||||||
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has |
Legend
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- Full support
- Full support
- See implementation notes.
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