JavaScript Spread and Rest

Spread Operator (...)

Copying Arrays

const arr1 = [1, 2, 3];
const arr2 = [...arr1]; // Copy

Combining Arrays

const arr1 = [1, 2];
const arr2 = [3, 4];
const combined = [...arr1, ...arr2]; // [1, 2, 3, 4]

Object Spread

const user = { name: 'John', age: 25 };
const updated = { ...user, age: 26 };

Rest Operator

function sum(...numbers) {
  return numbers.reduce((a, b) => a + b, 0);
}

sum(1, 2, 3, 4); // 10

Key Takeaway

Spread expands arrays/objects. Rest collects arguments. Both use ... syntax. Essential for modern JavaScript.