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 or updates an entry in this map with a specified key and a value.
Try it
const map1 = new Map();
map1.set("bar", "foo");
console.log(map1.get("bar"));
// Expected output: "foo"
console.log(map1.get("baz"));
// Expected output: undefined
Syntax
js
set(key, value)
Parameters
key-
The key of the element to add to the
Mapobject. The key may be any JavaScript type (any primitive value or any type of JavaScript object). value-
The value of the element to add to the
Mapobject. The value may be any JavaScript type (any primitive value or any type of JavaScript object).
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 |