JavaScript Map Reference

A JavaScript Map stores elements as key-value pairs and can have both objects and primitive values as keys or values. When iterated, it preserves the insertion order of the elements.

You can create a JavaScript Map by:

Passing an Array to new Map()
Creating a Map and using Map.set()

Passing an Array to `new Map()`

Example: In this example, an array of key-value pairs is passed to the Map constructor to create a Map. Each sub-array [key, value] represents a key-value pair.

// Create a Map by passing an Array of key-value pairs to the Map constructor
const arrayMap = new Map([
    ['key1', 'value1'],
    ['key2', 'value2'],
    ['key3', 'value3']
]);
 
// Accessing values in the Map
console.log(arrayMap.get('key1'));  // Output: "value1"
console.log(arrayMap.get('key2'));  // Output: "value2"
console.log(arrayMap.get('key3'));  // Output: "value3"

Output

value1
value2
value3

Create a Map and use `Map.set()`

Example: In this example, an empty Map is created, and then key-value pairs are added using the Map.set() method. This approach is useful when you want to dynamically build a Map during runtime.

// Create an empty Map and use Map.set() to add key-value pairs
const setMap = new Map();
 
// Adding key-value pairs using Map.set()
setMap.set('name', 'John');
setMap.set('age', 25);
setMap.set('city', 'New York');
 
// Accessing values in the Map
console.log(setMap.get('name'));  // Output: "John"
console.log(setMap.get('age'));   // Output: 25
console.log(setMap.get('city'));  // Output: "New York"

Output

John
25
New York

what is Javascript Map and how to use it?Set in Javascript