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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.

The keys() method of Map instances returns a new map iterator object that contains the keys for each element in this map in insertion order.

Try it

const map = new Map();

map.set("0", "foo");
map.set(1, "bar");

const iterator = map.keys();

console.log(iterator.next().value);
// Expected output: "0"

console.log(iterator.next().value);
// Expected output: 1

Syntax

keys()

Parameters

None.

Return value

A new iterable iterator object.

Examples

Using keys()

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); // {}

Specifications

Specification
ECMAScript® 2026 Language Specification> # sec-map.prototype.keys>

Browser compatibility

	Desktop					Mobile							Server
	Chrome	Edge	Firefox	Opera	Safari	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	WebView Android	WebView on iOS	Bun	Deno	Node.js
`keys`	38	12	20	25	8	38	20	25	8	3.0	38	8	1.0.0	1.0	0.12.0