Map.prototype.set()

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()")}}

```js interactive-example 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-nolint
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()")}}