JavaScript Map()
Syntax & Examples

Map constructor

The Map constructor in JavaScript creates a new Map object.

Syntax of Map

There are 2 variations for the syntax of Map() constructor. They are:

1.
new Map()

This constructor creates a new Map object that is empty.

Returns value of type Map.

2.
new Map(iterable)

Parameters

ParameterOptional/RequiredDescription
iterableoptionalAn iterable (e.g., an array) whose elements are key-value pairs. Each key-value pair is added to the new Map object.

This constructor creates a new Map object using given iterable.

Returns value of type Map.


✐ Examples

1 Creating an empty Map

In JavaScript, we can create an empty Map object using the Map constructor without any arguments.

For example,

  1. Create a new empty Map object using the new Map() syntax.
  2. Log the Map object to the console using console.log().

JavaScript Program

const map = new Map();
console.log(map);

Output

Map(0) {}

2 Creating a Map from an iterable

In JavaScript, we can create a Map object from an iterable (e.g., an array) containing key-value pairs using the Map constructor.

For example,

  1. Create an array items containing key-value pairs.
  2. Create a new Map object map using the new Map(iterable) syntax.
  3. Log the Map object to the console using console.log().

JavaScript Program

const items = [['a', 1], ['b', 2], ['c', 3]];
const map = new Map(items);
console.log(map);

Output

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

Summary

In this JavaScript tutorial, we learned about Map constructor of Map: the syntax and few working examples with output and detailed explanation for each example.