Map.prototype.set()
Baseline
Widely available
This feature is well established and works across many devices and browser versions. Itâs been available across browsers since â¨July 2015â©.
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.
Try it
const map = new Map();
map.set("bar", "foo");
console.log(map.get("bar"));
// Expected output: "foo"
console.log(map.get("baz"));
// Expected output: undefined
Syntax
js
set(key, value)
Parameters
Return value
The Map object.
Examples
Using set()
js
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");
Using the set() with chaining
Since the set() method returns back the same Map object, you can chain the method call like below:
js
// Add new elements to the map with chaining.
myMap.set("bar", "foo").set(1, "foobar").set(2, "baz");
Specifications
| Specification |
|---|
| ECMAScript® 2026 Language Specification # sec-map.prototype.set |