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.
Thekeys() method ofMap instances returns a newmap 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: 1Syntax
js
keys()Parameters
None.
Return value
A newiterable iterator object.
Examples
Using 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); // 1console.log(mapIter.next().value); // {}Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-map.prototype.keys |