files/en-us/web/javascript/reference/global_objects/map/set/index.md

metadata

title: Map.prototype.set()
short-title: set()
slug: Web/JavaScript/Reference/Global_Objects/Map/set
page-type: javascript-instance-method
browser-compat: javascript.builtins.Map.set
sidebar: jsref

The set() method of {{jsxref("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.

{{InteractiveExample("JavaScript Demo: Map.prototype.set()")}}

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

set(key, value)

Parameters

• key
  • : The 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.
• value
  • : The value of the entry to add to or modify within the Map object. Can be any value.

Return value

The Map object.

Examples

Using set()

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:

// Add new elements to the map with chaining.
myMap.set("bar", "foo").set(1, "foobar").set(2, "baz");

Specifications

{{Specifications}}

Browser compatibility

{{Compat}}

See also

• {{jsxref("Map")}}
• {{jsxref("Map.prototype.delete()")}}
• {{jsxref("Map.prototype.get()")}}
• {{jsxref("Map.prototype.has()")}}