Map Object

The Map object in JavaScript holds key-value pairs and remembers the original insertion order of the keys. Any value (both objects and primitive values) may be used as either a key or a value.

1. Creating a Map

You can create a map using the Map constructor:

const map = new Map([
    ['key1', 'value1'],
    ['key2', 'value2'],
    ['key3', 'value3']
]);
console.log(map); // Outputs: Map(3) { 'key1' => 'value1', 'key2' => 'value2', 'key3' => 'value3' }

2. Adding and Deleting Elements

You can add and delete elements from a map using the set() and delete() methods:

const map = new Map();
map.set('key1', 'value1');
map.set('key2', 'value2');
console.log(map); // Outputs: Map(2) { 'key1' => 'value1', 'key2' => 'value2' }

map.delete('key1');
console.log(map); // Outputs: Map(1) { 'key2' => 'value2' }

3. Checking for Elements

You can check if a map contains a specific key using the has() method:

const map = new Map([['key1', 'value1'], ['key2', 'value2']]);
console.log(map.has('key1')); // Outputs: true
console.log(map.has('key3')); // Outputs: false

4. Getting Values

You can get the value associated with a specific key using the get() method:

const map = new Map([['key1', 'value1'], ['key2', 'value2']]);
console.log(map.get('key1')); // Outputs: 'value1'
console.log(map.get('key3')); // Outputs: undefined

5. Iterating Over a Map

You can iterate over the elements of a map using the for...of loop:

const map = new Map([['key1', 'value1'], ['key2', 'value2']]);
for (let [key, value] of map) {
    console.log(key + ': ' + value);
}
// Outputs: 
// key1: value1
// key2: value2

6. Converting a Map to an Array

You can convert a map to an array using the Array.from() method or the spread operator:

const map = new Map([['key1', 'value1'], ['key2', 'value2']]);
const array = Array.from(map);
console.log(array); // Outputs: [['key1', 'value1'], ['key2', 'value2']]

const array2 = [...map];
console.log(array2); // Outputs: [['key1', 'value1'], ['key2', 'value2']]

7. Map Operations

Maps support various operations like clearing all elements and getting the size of the map:

const map = new Map([['key1', 'value1'], ['key2', 'value2']]);

// Size
console.log(map.size); // Outputs: 2

// Clear
map.clear();
console.log(map); // Outputs: Map(0) {}