Map.prototype[Symbol.iterator]()

{{JSRef}}

The [Symbol.iterator]() method of {{jsxref("Map")}} instances implements the iterable protocol and allows Map objects to be consumed by most syntaxes expecting iterables, such as the spread syntax and {{jsxref("Statements/for...of", "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 {{jsxref("Map.prototype.entries")}} property.

{{InteractiveExample("JavaScript Demo: Map.prototype[Symbol.iterator]()")}}

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 {{jsxref("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

{{Specifications}}

Browser compatibility

{{Compat}}

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