Sets

• A JavaScript Set is a collection of unique values.
• Each value can only occur once in a Set.

// Create a Set
const letters = new Set();

// Add Values to the Set
letters.add("a");
letters.add("b");
letters.add("c");

letters.forEach (function(value) {  
	console.log(value);  
})
for (const x of letters.values()) {  
	console.log(x);  
}

Important Methods

• size: Returns the number of elements in a Set
• add: Adds a new element to the Set
• delete: Removes an element from a Set
• has: Returns true if a value exists in the Set
• forEach: Invokes a callback for each element in the Set
• values: Returns an iterator with all the values in a Set

WeakSet

• You can only add objects to WeakSet (not primitives).
• If there are no other references to the object in weakset, it will be removed from memory and from the weakset automatically.
• It supports add, has and delete, but not size, keys() and no iterations.

let users = new WeakSet();
let user1 = {name: "ganesh"};
users.add(user1);
let user2 = {name: "siva"};
users.add(user2);

user2 = null;