files/en-us/web/javascript/reference/global_objects/map/keys/index.md

metadata

title: Map.prototype.keys()
short-title: keys()
slug: Web/JavaScript/Reference/Global_Objects/Map/keys
page-type: javascript-instance-method
browser-compat: javascript.builtins.Map.keys
sidebar: jsref

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

{{InteractiveExample("JavaScript Demo: Map.prototype.keys()")}}

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

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• {{jsxref("Map.prototype.entries()")}}
• {{jsxref("Map.prototype.values()")}}