Map.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.

Map 实例的 has() 方法返回一个布尔值,指示具有指定键的元素是否存在。

尝试一下

const map1 = new Map();
map1.set("bar", "foo");

console.log(map1.has("bar"));
// Expected output: true

console.log(map1.has("baz"));
// Expected output: false

语法

js
has(key)

参数

key

用于测试 Map 对象中是否存在的元素的键。

返回值

如果 Map 对象中存在具有指定键的元素,则返回 true;否则返回 false

示例

使用 has()

js
const myMap = new Map();
myMap.set("bar", "foo");

console.log(myMap.has("bar")); // true
console.log(myMap.has("baz")); // false

规范

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

浏览器兼容性

Report problems with this compatibility data on GitHub
desktopmobileserver
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
Deno
Node.js
has

Legend

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Full support
Full support

参见