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.

Map 实例的 keys() 方法返回一个新的 map 迭代器对象，该对象包含了此 map 中每个元素的键，按插入顺序排列。

尝试一下

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

语法

js
keys()

参数

无。

返回值

一个新的可迭代迭代器对象。

示例

使用 keys()

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); // {}

规范

Specification
ECMAScript® 2025 Language Specification
# sec-map.prototype.keys

浏览器兼容性

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参见