Map.prototype[Symbol.iterator]() - JavaScript

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iterable protocol and allows Map objects to be consumed by most syntaxes expecting iterables, such as the map iterator object that yields the key-value pairs of the map in insertion order.

The initial value of this property is the same function object as the initial value of the Map.prototype.entries property.

Try it

const map1 = new Map();

map1.set("0", "foo");
map1.set(1, "bar");

const iterator1 = map1[Symbol.iterator]();

for (const item of iterator1) {
  console.log(item);
}
/ Expected output: Array ["0", "foo"]
/ Expected output: Array [1, "bar"]

Syntax

map[Symbol.iterator]()

Parameters

None.

Return value

The same return value as iterable, and iterating syntaxes like the for...of loop automatically call this method to obtain the iterator to loop over.

const myMap = new Map();
myMap.set("0", "foo");
myMap.set(1, "bar");
myMap.set({}, "baz");

for (const entry of myMap) {
  console.log(entry);
}
/ ["0", "foo"]
/ [1, "bar"]
/ [{}, "baz"]

for (const [key, value] of myMap) {
  console.log(`${key}: ${value}`);
}
/ 0: foo
/ 1: bar
/ [Object]: baz

Manually hand-rolling the iterator

You may still manually call the next() method of the returned iterator object to achieve maximum control over the iteration process.

const myMap = new Map();
myMap.set("0", "foo");
myMap.set(1, "bar");
myMap.set({}, "baz");

const mapIter = myMap[Symbol.iterator]();

console.log(mapIter.next().value); / ["0", "foo"]
console.log(mapIter.next().value); / [1, "bar"]
console.log(mapIter.next().value); / [Object, "baz"]

Specifications

Specification
ECMAScript® 2026 Language Specification # sec-map.prototype-%symbol.iterator%