JavaScript provides built-in collection types for storing groups of values:

• Map
• Set
• WeakMap
• WeakSet

These offer better performance, flexibility, and functionality than regular objects and arrays for certain use cases.

A Map is a collection of key-value pairs, similar to objects, but with more features.

• Keys can be of any data type (including objects, functions, etc.)
• Maintains the insertion order
• Can easily get the size

const myMap = new Map();
myMap.set("name", "Varun");
myMap.set(1, "One");
myMap.set(true, "Boolean");

console.log(myMap.get("name"));  // "Varun"
console.log(myMap.size);         // 3

for (let [key, value] of myMap) {
    console.log(key, value);
}

A Set is a collection of unique values.

• Stores only unique values
• Can hold values of any type
• Maintains insertion order

const mySet = new Set();
mySet.add(1);
mySet.add(2);
mySet.add(2); // ignored, already exists

console.log(mySet.has(1));   // true
console.log(mySet.size);     // 2

mySet.forEach(value => console.log(value));

A WeakMap is like a Map, but:

• Keys must be objects
• Keys are weakly referenced (not prevented from garbage collection)

• Can't iterate or check size
• Great for storing private data tied to DOM elements or objects
• Helps avoid memory leaks

const wm = new WeakMap();
let obj = {};

wm.set(obj, "private value");
console.log(wm.get(obj)); // "private value"

obj = null; // Now the key-value pair is eligible for garbage collection

⚠️ WeakMap methods: set, get, has, delete

A WeakSet is like a Set, but:

• Only stores objects
• Objects are held weakly
• Not iterable

• Cannot check size or iterate
• Useful for managing object references without memory leaks

const ws = new WeakSet();
let user = { name: "Varun" };

ws.add(user);
console.log(ws.has(user)); // true

user = null; // Automatically removed from the WeakSet

• Store usernames uniquely → Set
• Cache user metadata → Map
• Track element-specific data safely → WeakMap
• Track whether objects were seen → WeakSet

• Use Map/Set when you need iteration and full data control
• Use WeakMap/WeakSet when dealing with temporary object references and memory-sensitive operations

Happy Coding! 🚀