spread operator

The spread operator (...) in JavaScript is a versatile and powerful feature that allows you to expand or spread elements in arrays, objects, or function arguments. It’s commonly used for copying, merging, and passing around data structures without modifying the original ones.

the use of spread operator in Array

Copying an Array:

const arr1 = ["Apple","Banana", "Orange"];
const arr2 = [...arr1];
console.log(arr2); // Output: [Apple,Banana,"Orange]

Combining Arrays

const arr1 = [1, 2, 3];
const arr2 = [4, 5, 6];
const combined = [...arr1, ...arr2];
console.log(combined); // Output: [1, 2, 3, 4, 5, 6]

Adding Elements to an Array:

const arr1 = [1, 2, 3];
const arr2 = [0, ...arr1, 4];
console.log(arr2); // Output: [0, 1, 2, 3, 4]

the use of the spread operator in Object

Copying an Object

const obj1 = { name: 'John', age: 38 };
const obj2 = { ...obj1 };
console.log(obj2); // Output: {name: 'John', age: 38}

Merging Objects

const obj1 = { name: 'John', age: 38 };
const obj2 = { sex: 'Male', qualification: 'Graduate'};
const merged = { ...obj1, ...obj2 };
console.log(merged); // Output: {name: 'John', age: 38, sex: 'Male', qualification: 'Graduate' }

Overriding Properties

const obj1 = { name: 'John', age: 38 };
const obj2 = { age: 39, qualification: 'Graduate'};
const merged = { ...obj1, ...obj2 };
console.log(merged); // Output: {name: 'John', age: 39, qualification: 'Graduate' }

Function Arguments

Spreading an Array as Arguments

function sum(a, b, c, d) {
  return a+b+c+d;
}
const numbers = [1, 2, 3,4];
console.log(sum(...numbers)); // Output: 10

spread operator – Interview Questions

spread operator – Objective Questions (MCQs)