Map.prototype.set()
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 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 |
Browser compatibility
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