JavaScript Interview Question #24

What is the spread syntax in JavaScript?

JavaScript Fundamentals, Types, Scope & Functions Junior Beginner

Quick Interview Answer

Spread syntax uses three dots to expand an iterable into individual elements or to copy enumerable properties into a new object. It is commonly used with arrays, function arguments, and object literals.

Detailed Explanation

Spread performs a shallow copy, not a deep clone. If a copied array or object contains nested objects, the nested references are still shared unless they are separately copied.

Code Example

const first = [1, 2];
const second = [...first, 3, 4];

const user = { name: "Asif", city: "Multan" };
const updated = { ...user, city: "Lahore" };

console.log(second);
console.log(updated);