JavaScript Maps

In JavaScript, a Map is a built-in data structure that allows for storing key-value pairs where both the keys and values can be of any data type

Map Methods

Method	Description
new Map()	Creates a new Map
set()	Sets the value for a key in a Map
get()	Gets the value for a key in a Map
delete()	Removes a Map element specified by the key
has()	Returns true if a key exists in a Map
forEach()	Calls a function for each key/value pair in a Map
entries()	Returns an iterator with the [key, value] pairs in a Map

new Map()

You can create a Map by passing an Array to the new Map() constructor:

Example

    let myMap = new Map([
    ['key1', 'value1'],
    ['key2', 'value2'],
    ['key3', 'value3']
]);

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Output

set()

You can add elements to a Map with the set() method:

Example

let myMap = new Map();

// Adding key-value pairs to the Map
myMap.set('name', 'John');
myMap.set('age', 30);

// Updating the value associated with an existing key
myMap.set('age', 35);

// Adding a new key-value pair
myMap.set('country', 'USA');

console.log(myMap);

get()

The get() method gets the value of a key in a Map:

Example

let myMap = new Map();

myMap.set('name', 'John');
myMap.set('age', 30);
myMap.set('country', 'USA');

console.log(myMap.get('name')); // Output: John
console.log(myMap.get('age'));  // Output: 30
console.log(myMap.get('city')); // Output: undefined (key 'city' does not exist)

delete()

The delete() method removes a Map element:

Example

let myMap = new Map();

myMap.set('name', 'John');
myMap.set('age', 30);
myMap.set('country', 'USA');

console.log(myMap.delete('age')); // Output: true (the key 'age' was present and deleted)
console.log(myMap.delete('city')); // Output: false (the key 'city' was not present)
console.log(myMap); // Output: Map(2) { 'name' => 'John', 'country' => 'USA' }

has()

The has() method returns true if a key exists in a Map:

Example

let myMap = new Map();

myMap.set('name', 'John');
myMap.set('age', 30);
myMap.set('country', 'USA');

console.log(myMap.has('name')); // Output: true (the key 'name' is present)
console.log(myMap.has('city')); // Output: false (the key 'city' is not present)

foreach()

The forEach() method calls a function for each key/value pair in a Map:

Example

let myMap = new Map();

myMap.set('name', 'John');
myMap.set('age', 30);
myMap.set('country', 'USA');

myMap.forEach((value, key) => {
    console.log(key + ': ' + value);
});

entries()

The entries() method returns an iterator object with the [key, values] in a Map:

Example

let myMap = new Map();

myMap.set('name', 'John');
myMap.set('age', 30);
myMap.set('country', 'USA');

let iterator = myMap.entries();
console.log(iterator.next().value); // Output: ['name', 'John']
console.log(iterator.next().value); // Output: ['age', 30]
console.log(iterator.next().value); // Output: ['country', 'USA']

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