Sets

Set ek collection hai jiska ek hi defining rule hai: usme har value unique hoti hai. Duplicate add karo to kuch nahi hota — woh pehle se hi wahan hai.

let numbers = new Set([1, 2, 3, 2, 1]);
console.log(numbers);

numbers.add(4);
console.log(numbers);

console.log(numbers.has(2));
console.log(numbers.size);

Set { 1, 2, 3 }
Set { 1, 2, 3, 4 }
true
4

new Set([1, 2, 3, 2, 1]) bante hi sirf teen unique values mein collapse ho jaata hai. has() membership check karta hai, aur size (length nahi) count deta hai.

Set aur array ke beech convert karna

Sets mein map() ya filter() jaise array methods directly nahi hote — jab woh chahiye ho to spread syntax [...set] use karke convert karo.

let unique = [...new Set([1, 1, 2, 2, 3])];
console.log(unique);

[ 1, 2, 3 ]

Yeh genuinely useful hai, sirf ek novelty nahi: array ko deduplicate karna exactly yahi pattern hai — duplicates hatane ke liye ise Set mein wrap karo, phir wapas ek plain array mein spread kar do.

Aage: conditional statements — apne code ko actually ek value ke basis par branch karwana.