JavaScript Introduction

JavaScript

JavaScript is the programming language of the web. It makes websites interactive — buttons that click, forms that validate, content that updates without reloading.

What Can JavaScript Do?

Change HTML content and styles
React to user events (clicks, typing)
Validate form data
Create animations and games
Build full applications (React, Node.js)

Example — JAVASCRIPT

// Show a message
alert("Hello, World!");

// Change page content
document.getElementById("demo")
    .innerHTML = "JavaScript is fun!";

// Log to console (for debugging)
console.log("Page loaded!");

// Simple calculation
let price = 100;
let tax = price * 0.18;
console.log("Tax: ₹" + tax);

Result

▶ Alert: "Hello, World!"
▶ Element updated: "JavaScript is fun!"
▶ Console: "Page loaded!"
▶ Console: "Tax: ₹18"

NextJavaScript Variables

Interview Questions — JavaScript Introduction

5 questions commonly asked in interviews

Q1 What is JavaScript? Beginner

JavaScript is a programming language used to add interactivity to web pages such as animations, form validation, and dynamic content updates.

Q2 Where is JavaScript used? Beginner

JavaScript is used in web browsers, servers (Node.js), mobile apps, and even desktop applications.

Q3 What is the difference between JavaScript and HTML? Beginner

HTML structures the content, while JavaScript adds behavior and interactivity.

Q4 What is a script tag? Beginner

The <script> tag is used to include JavaScript inside an HTML page.

Q5 What is an event in JavaScript? Intermediate

An event is an action like a click, hover, or key press that triggers JavaScript code.

Frequently Asked Questions

Common doubts about JavaScript Introduction

No, JavaScript and Java are completely different languages.

Yes, using Node.js.

Yes, it is beginner-friendly and widely used.

Yes, it can dynamically change HTML content.

Yes, for interactive and dynamic websites.

Test Your Knowledge

5 questions · Earn 50 XP

0 / 5

Q1 JavaScript is used for?

Q2 Which tag is used for JS?

Q3 JS runs in?

Q4 Which is JS file extension?

Q5 JS is?

More on JavaScript Introduction

Cheatsheet, tips, resources & what to learn next

Quick Cheatsheet

Inline JS

<button onclick="alert('Hi')">Click</button>

Script Tag

<script>console.log(\"Hello\");</script>

External JS

<script src="app.js"></script>

Alert

alert(\"Hello World\");

Console

console.log(\"Debug\");

Pro Tips

Use console.log for debugging.

Keep JS in external files.

Avoid inline JS in large apps.

Use browser dev tools.

Practice small scripts daily.

Resources

MDN JS Basics Docs

W3Schools JS Practice

freeCodeCamp JS Practice

JavaScript Info Docs

JS Course Video

Up Next

JS Variables JS Data Types JS Functions JS Events JS DOM