Number.isNaN() — JS Technical Interview Questions & Answers

Checks whether a value is NaN, without type coercion.

Number.isNaN()

  • Number.isNaN() is a JS topic. In plain words you use it for a short Number.isNaN example in a script in the browser. Don’t start with a slogan — start with that picture.
  • Smallest example: the smallest Number.isNaN example you can type. Type it, run it, and say what you see. If you can do that from memory, you know Number.isNaN().
  • From the example next to this theory: Checks whether a value is NaN, without type coercion.
  • Trap: only saying “Number.isNaN” with no example. Fix that before you talk about advanced JS.
  • Viva: what is Number.isNaN()? Then show the smallest Number.isNaN example you can type. Then name the trap.

Technical Interview Tip: What is Number.isNaN()? Show this: the smallest Number.isNaN example you can type. Trap: only saying “Number.isNaN” with no example.

Code Examples for Number.isNaN()

Number.isNaN() — working example

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

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

How to Explain Number.isNaN() to an Interviewer

What is Number.isNaN()?

Used for a short Number.isNaN example a script in the browser Not just the heading

Give one small example of Number.isNaN().

the smallest Number.isNaN example you can type Checks whether a value is NaN, without type coercion

What mistake do beginners make with Number.isNaN()?

only saying “Number.isNaN” with no example Show the fix

Where do you use Number.isNaN()?

a script in the browser a short Number.isNaN example