Object.keys() — JS Technical Interview Questions & Answers

Returns an array of an object's own enumerable keys.

Object.keys()

  • Object.keys() is a JS topic. In plain words you use it for { name, marks } in a student record. Don’t start with a slogan — start with that picture.
  • Smallest example: const { name } = student. Type it, run it, and say what you see. If you can do that from memory, you know Object.keys().
  • From the example next to this theory: Returns an array of an object's own enumerable keys.
  • Trap: copying nested objects by accident (shallow copy). Fix that before you talk about advanced JS.
  • Viva: what is Object.keys()? Then show const { name } = student. Then name the trap.

Technical Interview Tip: What is Object.keys()? Show this: const { name } = student. Trap: copying nested objects by accident (shallow copy).

Code Examples for Object.keys()

Object.keys() — working example

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

Object.keys(): map then reduce on [1, 2, 3]. Say both prints.

How to Explain Object.keys() to an Interviewer

What is Object.keys()?

Used for { name, marks } a student record Not just the heading

Give one small example of Object.keys().

const { name } = student Returns an array of an object's own enumerable keys

What mistake do beginners make with Object.keys()?

copying nested objects by accident (shallow copy) Show the fix

Where do you use Object.keys()?

a student record { name, marks }