Map.prototype[Symbol.iterator]() - JavaScript | MDN
Try it
const map = new Map();
map.set("0", "foo");
map.set(1, "bar");
const iterator = map[Symbol.iterator]();
for (const item of iterator) {
console.log(item);
}
// Expected output: Array ["0", "foo"]
// Expected output: Array [1, "bar"]
Syntax
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.
js
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.
js
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® 2027 Language Specification # sec-map.prototype-%symbol.iterator% |