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Map.prototype.has() - JavaScript | MDN
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Map.prototype.has()

Baseline Widely available

This feature is well established and works across many devices and browser versions. Its been available across browsers since 2015 7.

Map has() .

In this article

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

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

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

js
has(key)

key

Map

Map true, false

has()

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

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

Specification
ECMAScript 2027 LanguageSpecification
# sec-map.prototype.has

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