Higher-Order Functions — JS Technical Interview Questions & Answers

Functions that take or return other functions.

Higher-Order Functions

  • Higher-Order Functions (js) is a JS topic. In plain words you use it for add(a, b) in a checkout total. Don’t start with a slogan — start with that picture.
  • Smallest example: function add / const add = () =>. Type it, run it, and say what you see. If you can do that from memory, you know Higher-Order Functions (js).
  • From the example next to this theory: Functions that take or return other functions.
  • Trap: this surprise in arrow vs function. Fix that before you talk about advanced JS.
  • Viva: what is Higher-Order Functions (js)? Then show function add / const add = () =>. Then name the trap.

Technical Interview Tip: What is Higher-Order Functions (js)? Show this: function add / const add = () =>. Trap: this surprise in arrow vs function.

Code Examples for Higher-Order Functions

Higher-Order Functions — working example

function makeCounter() {
  let n = 0;
  return function () {
    n += 1;
    return n;
  };
}
const next = makeCounter();
console.log(next(), next(), next()); // 1 2 3

function makeAdder(x) {
  return (y) => x + y;
}
console.log(makeAdder(5)(3));

Higher-Order Functions — a closure remembers variables from its outer scope after that scope finished.

How to Explain Higher-Order Functions to an Interviewer

What is Higher-Order Functions (js)?

Used for add(a, b) a checkout total Not just the heading

Give one small example of Higher-Order Functions (js).

function add / const add = () => Functions that take or return other functions

What mistake do beginners make with Higher-Order Functions (js)?

this surprise in arrow vs function Show the fix

Where do you use Higher-Order Functions (js)?

a checkout total add(a, b)