Callbacks — Node.js Technical Interview Questions & Answers

Callbacks

Callbacks

  • Callbacks is a Node.js topic. In plain words you use it for read notes.txt in a script. Don’t start with a slogan — start with that picture.
  • Smallest example: (err, data) => …. Type it, run it, and say what you see. If you can do that from memory, you know Callbacks.
  • From the example next to this theory: Callbacks: find user 2, then list names.
  • Trap: callback hell, no error-first. Fix that before you talk about advanced Node.js.
  • Viva: what is Callbacks? Then show (err, data) => …. Then name the trap.

Technical Interview Tip: What is Callbacks? Show this: (err, data) => …. Trap: callback hell, no error-first.

Code Examples for Callbacks

Callbacks — working example

// Callbacks
const users = [
  { id: 1, name: "Asha" },
  { id: 2, name: "Ravi" },
];

function findUser(id) {
  return users.find((u) => u.id === id) ?? null;
}

console.log(findUser(2));
console.log(users.map((u) => u.name));

Callbacks: find user 2, then list names. Say both prints.

How to Explain Callbacks to an Interviewer

What is Callbacks?

Used for read notes.txt a script Not just the heading

Give one small example of Callbacks.

(err, data) => … Callbacks: find user 2, then list names

What mistake do beginners make with Callbacks?

callback hell, no error-first Show the fix

Where do you use Callbacks?

a script read notes.txt