What are Map and Set, and how do they differ?

Map and Set are built-in data structures in JavaScript (and Node.js) designed for storing collections of data with specific properties.

Map is a collection of key-value pairs, where keys can be of any type (objects, primitives, etc.). Unlike a regular object, Map preserves the insertion order of elements and provides methods for convenient manipulation.

Set is a collection of unique values of any type. Duplicates are not allowed in Set, and it also maintains insertion order.

Main differences:

• Map stores key-value pairs, Set only stores unique values.
• In Map, keys can be of any type; in Set, only values.
• Map has methods get, set, has, delete, while Set has add, has, delete.

Example usage:

const map = new Map();
map.set('key1', 'value1');
map.set({}, 'value2');
console.log(map.get('key1')); // 'value1'

const set = new Set();
set.add(1);
set.add(2);
set.add(1); // will not be added again, since 1 already exists
console.log(set.has(1)); // true