My Node.js - First Interview Experience & Important Concepts!

#javascript #career #webdev #node

Hello, friends!!

Today I attended my first Node.js interview round as part of my backend development journey. Since Node.js is closely related to JavaScript, most of the interview questions covered both JavaScript and Node.js basics.

This interview made me realize how important it is to understand core concepts before diving deeper into backend development.

Let me share what I learned and some important topics with short explanations!!

JavaScript & Node.js Topics from the Interview:

1.Function Declaration vs Function Expression:

Declaration: You can call the function before it's defined (hoisting).
Expression: Stored in a variable; cannot call before definition.

2.setTimeout() in JavaScript:

Executes a function after a delay (in milliseconds).

Example:

setTimeout(() => { console.log("Hello after 2 seconds"); }, 2000);

3.Selecting Elements from DOM:

Example:

document.getElementById('id');  
document.querySelector('.class');

4.Async/Await in JS:

Makes asynchronous code look synchronous and clean.
Used with Promises.

5.Callback Function:

A function passed as an argument to another function and executed later.

6.What is Node.js?

Runtime environment to run JS outside the browser.
Uses Google’s V8 Engine.

7.Why Node.js uses V8 Engine?

V8 makes JS execution fast and efficient.

8.Why Node.js is Single-threaded?

Handles tasks using Event Loop and Non-blocking I/O, so no need for multiple threads.

9.Can you access DOM in Node.js?

❌ No, because Node.js runs on the server, not in the browser.

10.Simple HTTP Server in Node.js:

const http = require('http');
http.createServer((req, res) => {
  res.write('Hello World');
  res.end();
}).listen(3000);

11.Synchronous vs Asynchronous Functions:

Synchronous: Blocks execution.
Asynchronous: Does not block execution.

12.HTTP Methods:

GET, POST, PUT, DELETE.

13.‘this’ Keyword in JavaScript

Refers to the current object.
In global scope: window object (browser).

14.undefined vs null

undefined: Variable declared but not assigned.
null: Assigned as "no value".

15.== vs ===

== compares only value (type conversion).
=== compares value + type (strict).

16.Truthy & Falsy Values:

Falsy: 0, "", null, undefined, NaN, false.
Everything else is truthy.

17.Global vs Local Scope

Global: Accessible everywhere.
Local: Accessible only inside functions or blocks.

18.Startup vs Big Companies - My Preference:

1.Startups = Learning, Growth, Multi-tasking
2.Big Companies = Stability, Process, Big Teams
3.For now, I prefer startups to learn and grow fast!