shift() and unshift() — JS Technical Interview Questions & Answers

Adding/removing elements at the start of an array.

shift() and unshift()

  • shift() and unshift() (array) is a JS topic. In plain words you use it for fail students only in a marks list. Don’t start with a slogan — start with that picture.
  • Smallest example: filter(m => m < 40). Type it, run it, and say what you see. If you can do that from memory, you know shift() and unshift() (array).
  • From the example next to this theory: Adding/removing elements at the start of an array.
  • Trap: mutating while filtering. Fix that before you talk about advanced JS.
  • Viva: what is shift() and unshift() (array)? Then show filter(m => m < 40). Then name the trap.

Technical Interview Tip: What is shift() and unshift() (array)? Show this: filter(m => m < 40). Trap: mutating while filtering.

Code Examples for shift() and unshift()

shift() and unshift() — working example

// Topic: shift() and unshift()
const nums = [1, 2, 3];
const doubled = nums.map((n) => n * 2);
console.log(doubled);
console.log(doubled.reduce((a, b) => a + b, 0));

shift() and unshift(): map then reduce on [1, 2, 3]. Say both prints.

How to Explain shift() and unshift() to an Interviewer

What is shift() and unshift() (array)?

Used for fail students only a marks list Not just the heading

Give one small example of shift() and unshift() (array).

filter(m => m < 40) Adding/removing elements at the start of an array

What mistake do beginners make with shift() and unshift() (array)?

mutating while filtering Show the fix

Where do you use shift() and unshift() (array)?

a marks list fail students only