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WeakSet.prototype.has() - JavaScript | MDN
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WeakSet.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 2015年9月.
has() メソッドは、特定の値をもつ要素が WeakSet オブジェクト内に存在するかどうかを示す真偽値を返します。
試してみましょう
const weakset1 = new WeakSet();
const object1 = {};
const object2 = {};
weakset1.add(object1);
console.log(weakset1.has(object1));
// Expected output: true
console.log(weakset1.has(object2));
// Expected output: false
構文
ws.has(value);
引数
value-
WeakSetオブジェクトに存在するかテストする値です。
返値
- Boolean
-
WeakSetオブジェクト内に特定の値をもつ要素が存在していたらtrueを返します。さもなければfalseを返します。
例
has() メソッドの使用
js
var ws = new WeakSet();
var obj = {};
ws.add(window);
mySet.has(window); // returns true
mySet.has(obj); // returns false
仕様書
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-weakset.prototype.has |
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