Map.prototype[Symbol.iterator]()
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 [Symbol.iterator]() method of Map instances implements the iterable protocol and allows Map objects to be consumed by most syntaxes expecting iterables, such as the spread syntax and for...of loops. It returns a 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.
Example
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 Map.prototype.entries(): a new iterable iterator object that yields the key-value pairs of the map.
Examples
Iteration using for...of loop
Note that you seldom need to call this method directly. The existence of the [Symbol.iterator]() method makes Map objects 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® 2025 Language Specification # sec-map.prototype-%symbol.iterator% |
Browser compatibility
| desktop | mobile | server | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
[Symbol.iterator] | ||||||||||||||