JavaScript Map() Constructor (original) (raw)

Last Updated : 23 Jul, 2025

The **Map() **constructoris used to create Map objects in JavaScript. The map is a data structure that stores elements as a key, value pair.

**Syntax:

new Map()
new Map(iterable)

**Parameters:

• **iterable: An iterable object used for iterating through elements, stored as a key, value pair.

**Return value:

• A new Map object returns after the initialization of the map constructor.

**Example 1:

JavaScript `

// map1 contains // 1 => 10 // 2 => 20 // 3 => 30 // 4 => 40 let map1 = new Map([ [1, 10], [2, 20], [3, 30], [4, 40] ]);

console.log("Map1: "); console.log(map1);

`

**Output:

Map1:
Map(4) { 1 => 10, 2 => 20, 3 => 30, 4 => 40 }

**Example 2:

JavaScript `

// map2 contains // firstname => Ram // lastname => Prasad // website => geeksforgeeks let map2 = new Map([ ["firstname", "Ram"], ["lastname", "Prasad"], ["website", "geeksforgeeks"] ]);

console.log("Map2: "); console.log(map2);

`

**Output:

Map2:
Map(3) {
'firstname' => 'Ram',
'lastname' => 'Prasad',
'website' => 'geeksforgeeks'
}

**Example 3:

JavaScript `

// Map contains nested array let map3 = new Map([ ["whole numbers", [1, 2, 3, 4]], ["Decimal numbers", [1.1, 1.2, 1.3, 1.4]], ["negative numbers", [-1, -2, -3, -4]] ]);

console.log("Map3: "); console.log(map3);

`

**Output:

Map3:
Map(3) {
'whole numbers' => [ 1, 2, 3, 4],
'Decimal numbers' => [ 1.1, 1.2, 1.3, 1.4],
'negative numbers' => [ -1, -2, -3, -4]
}

**Supported Browsers:

• Chrome 38
• Edge 12
• Firefox 13
• Opera 25
• Safari 8