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This feature is well established and works across many devices and browser versions. Its been available across browsers since July 2015.
The set() method of Map instances adds a new entry with a specified key and value to this Map, or updates an existing entry if the key already exists.
const map = new Map();
map.set("bar", "foo");
console.log(map.get("bar"));
// Expected output: "foo"
console.log(map.get("baz"));
// Expected output: undefined
set(key, value)
keyThe key of the entry to add to or modify within the Map object. Can be any value. Object keys are compared by reference, not by value.
valueThe value of the entry to add to or modify within the Map object. Can be any value.
The Map object.
const myMap = new Map();
// Add new elements to the map
myMap.set("bar", "foo");
myMap.set(1, "foobar");
// Update an element in the map
myMap.set("bar", "baz");
Since the set() method returns back the same Map object, you can chain the method call like below:
// Add new elements to the map with chaining.
myMap.set("bar", "foo").set(1, "foobar").set(2, "baz");
| Specification |
|---|
| ECMAScript 2027 LanguageSpecification # sec-map.prototype.set |
This page was last modified on Sep 22, 2025 by MDN contributors.
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