Map.prototype.keys()
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.
試してみましょう
const map1 = new Map(); map1.set("0", "foo"); map1.set(1, "bar"); const iterator1 = map1.keys(); console.log(iterator1.next().value); // Expected output: "0" console.log(iterator1.next().value); // Expected output: 1 構文
js
keys() 引数
なし。
返値
新しい反復可能なイテレーターオブジェクトです。
例
keys() の使用
js
const myMap = new Map(); myMap.set("0", "foo"); myMap.set(1, "bar"); myMap.set({}, "baz"); const mapIter = myMap.keys(); console.log(mapIter.next().value); // "0" console.log(mapIter.next().value); // 1 console.log(mapIter.next().value); // {} 仕様書
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-map.prototype.keys |
