JavaScript Map.set() Method

Map.set()

The Map.set() method in JavaScript is used to add or update key-value pairs in a Map object. If the key already exists, its value is updated; otherwise, a new key-value pair is added.

Syntax

map.set(key, value)

Parameters

Parameter	Description
key	The key to be added or updated in the Map.
value	The value associated with the specified key.

Return Value

The set() method returns the updated Map object, allowing method chaining.

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Examples

1. Adding Key-Value Pairs

This example demonstrates how to add key-value pairs to a Map.

const map = new Map();

map.set('name', 'Arjun');
map.set('age', 25);
map.set('city', 'New York');

console.log(map);

Output

Map(3) { 'name' => 'Arjun', 'age' => 25, 'city' => 'New York' }

1. set('name', 'Arjun') adds a key-value pair where 'name' is the key and 'Arjun' is the value.
2. Each call to set() updates the Map with a new entry.

2. Updating an Existing Key

If the key already exists, its value is updated instead of adding a new entry.

const map = new Map();

map.set('name', 'Arjun');
map.set('name', 'Bhairav'); // Updates the value for 'name'

console.log(map.get('name'));

Output

Bhairav

1. set('name', 'Arjun') initially adds the key-value pair.
2. set('name', 'Bhairav') updates the value associated with 'name'.

3. Using Non-String Keys

The Map object allows keys of any type, including objects and functions.

const map = new Map();

const objKey = { id: 1 };
const funcKey = () => {};

map.set(objKey, 'Object Value');
map.set(funcKey, 'Function Value');

console.log(map.get(objKey));
console.log(map.get(funcKey));

Output

Object Value
Function Value

The set() method successfully stores values with object and function keys.

4. Chaining set() Calls

Since set() returns the Map object, multiple calls can be chained together.

const map = new Map()
    .set('a', 1)
    .set('b', 2)
    .set('c', 3);

console.log(map);

Output

Map(3) { 'a' => 1, 'b' => 2, 'c' => 3 }

Chaining allows for cleaner and more readable code.