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JavaScript Tutorial - GeeksforGeeks

JavaScript Tutorial

Last Updated : 05 Jun, 2025

JavaScript is a programming language used to create dynamic content for websites. It is a lightweight, cross-platform, and single-threaded programming language. It's an interpreted language that executes code line by line, providing more flexibility.

JavaScript on Client Side: On the client side, JavaScript works along with HTML and CSS. HTML adds structure to a web page, CSS styles it, and JavaScript brings it to life by allowing users to interact with elements on the page, such as actions on clicking buttons, filling out forms, and showing animations. JavaScript on the client side is directly executed in the user's browser.
JavaScript on Server Side: On the Server side (on Web Servers), JavaScript is used to access databases, file handling, and security features to send responses, to browsers.

Why Learn JavaScript?

JavaScript is core language for web development, enabling dynamic and interactive features in websites with fewer lines of code.
It is highly in demand, offering many job opportunities in Frontend, Backend (Node.js), and Full Stack Development.
JavaScript supports powerful frameworks and libraries like React, Angular, Vue.js, Node.js, and Express.js, widely used in modern web applications.
JavaScript is an object-oriented and event-driven language, ideal for building scalable and responsive applications.
It is cross-platform and runs directly in all modern web browsers without the need for installation.
Major companies like Google, Facebook, and Amazon use JavaScript in their tech stacks.

Write and Run Your First JavaScript Program

Mostly browsers can run JavaScript directly, so there's no need to install a compiler. However, the built-in browser console isn’t very beginner-friendly. That’s why we’ve added an online editor below to help you get started easily.

JavaScript


 console.log("Hello World!");

Before we start, We recommend you to edit the code and try to print your own name.

Fundamentals

Let's Explore JavaScript's fundamentals which will help build you a understanding to start with JavaScript

Functions and Events

Functions in JavaScript are reusable blocks of code that perform a specific task. Events are actions that happen in the browser, such as mouse clicks, keyboard input, or page loading.

JavaScript Beginner Projects

Now you have a basic understanding of JavaScript. So start with some beginner level projects to clear your concept and to implement in real world applications.

JavaScript Data Structure

JavaScript provides a versatile set of data structures that help in efficient data storage, manipulation, and problem-solving. In this section, we will explore each data structure and algorithm in detail.

JavaScript's built-in utilities and ES6+ enhancements provide additional data structures, including the following

To learn data structure and algorithm with JavaScript in detail, you can refer to our DSA with JavaScript Tutorial.

Object Oriented Programming

Object-Oriented Programming (OOP) in JavaScript, a concept that enables the structure of code by modeling real-world entities as objects with properties and behaviors.

Browser and Document Object Model

Asynchronous JavaScript

Now you have a good understanding of JavaScript. So let's implement all these in some real world applications.

JavaScript JSON

It is a lightweight data format for storing and exchanging data widely used to send data between a server and a client.

Regular Expression and Validation

Regular expressions plays important role for validation. Validations help ensure that data entered by users meets specific criteria.

Exception and Error Handling

Exception and Error handling is crucial for ensuring the reliability and stability of JavaScript applications by handling errors effectively

Testing and Performance Optimization

Interesting Facts

This section covers all the interesting facts and features which made JavaScript so popular and will easy if you are switching from other programming languages also.

JavaScript Advanced Projects

Now you have covered almost all the important concepts of JavaScript. These projects will improve and revise your JavaScript Knowledge.

For all lists of Projects follow the article- JavaScript Project Ideas with Source Code

JavaScript Quiz

This section offers a collection of practice Quiz designed to test and support understanding of various concepts in JavaScript.

JavaScript Practice

The javaScript Coding Practice Problems page offers exercises for all skill levels, covering basic Numbers, String to advanced structures like Stack, Queue. These problems help build a strong foundation and boost confidence in solving real-world coding challenges.

Coding Problems

JavaScript Exercises

Interview Questions

This section provides a list of interview questions related to JavaScript.

For a quick recap of JavaScript read the article - JavaScript Cheat Sheet

Libraries and Frameworks

JavaScript libraries and frameworks play a important role in modern web development. They offer built-in functions and methods that enhance web pages, making them more dynamic and interactive. They handle repetitive tasks, allowing developers to focus on core functionality.

Also, they provide project structure and data flow structure that helps to create fast and more reliable applications.

JavaScript Tutorial- Libraries and Frameworks Libraries

Libraries provide pre-built solutions for common tasks. Developers can use these functions instead of writing code from scratch, saving valuable time. Here are a few popular libraries of JavaScript.

Frontend Libraries: React, Preact, Lodash, Moment.js, jQuery, Axios
Backend Libraries:Socket.io, JWT, Bcrypt, Passport.js, CORS

Frameworks

Frameworks, offer a comprehensive structure for building applications. Here are a few popular frameworks of JavaScript.

Frontend Frameworks:Vue.js, Angular, Next.js, Nuxt.js, Gatsby, Remix
Backend Frameworks:Express.js, NestJS, Koa.js, Sails.js, Fastify
FullStack FrameWorks:Meteor.js, Next.js, Nuxt.js, RedwoodJS

Features of JavaScript

JavaScript is one of the most widely used programming languages, known for its flexibility and versatility in web development. Here are some key features or characteristics:

Easy to Learn and Use: JavaScript's syntax is simple and straightforward, making it easy for both beginners and experienced developers to pick up.
Interpreted Language: JavaScript is an interpreted language, means it is executed directly by the browser without the need for a compiler.
Event-Driven and Asynchronous: JavaScript is designed to handle events, making it ideal for interactive web pages. It supports asynchronous programming, enabling non-blocking operations.
Object-Oriented and Functional: JavaScript supports both object-oriented and functional programming. This gives developers the flexibility to structure their code according to their need.
Dynamically Typed: In JavaScript, you don’t need to declare data types when declaring variables. The language automatically determines the data type at runtime, making it more flexible.
Extensive Libraries and Frameworks: JavaScript has a rich ecosystem of libraries and frameworks such as React, Angular, and Vue.js, which simplify and speed up development for both front-end and back-end projects.
Cross-Platform: JavaScript is supported across all modern browsers, allowing the same code to run seamlessly on different operating systems and platforms.
Large Community Support: JavaScript benefits from a large, active developer community that contributes to its growth. With numerous resources available, finding help or solutions is always easy.

Applications of JavaScript

JavaScript is a versatile language that powers various applications, from web development to mobile apps, making it an essential tool for modern programming.

Web Development: JavaScript is widely used in web development to create interactive and dynamic websites. Frameworks like React and Angular make front-end development faster, while Node.js is used for building server-side applications.
Mobile App Development: JavaScript helps in developing mobile apps using frameworks like React Native, allowing developers to build cross-platform apps for both iOS and Android.
Game Development: JavaScript is also used for creating browser-based games with libraries like Phaser, making it easy to develop 2D games that run directly in the browser.
Server-Side Development: With Node.js, JavaScript is used for server-side programming, enabling developers to build scalable applications and APIs, especially for real-time features like chat systems.
Scripting & Automation: JavaScript is ideal for automating web-related tasks like form validation and data manipulation, improving efficiency and reducing manual work.
Web Scraping: JavaScript, along with libraries like Puppeteer, is used to extract information from websites for data analysis or research, making it useful for web scraping tasks.
IoT (Internet of Things): JavaScript is used to control devices and sensors in IoT projects, allowing developers to build smart systems with frameworks like Johnny-Five.
Real-Time Applications: JavaScript powers real-time applications, such as live chats or notifications, using technologies like WebSockets and Socket.io for instant communication between users and servers.

JavaScript vs. Other Programming Languages

Below is a comparison of JavaScript with Python, C++, and Java:

Feature

JavaScript

Python

C++

Java

Type

Interpreted

Compiled

Compiled and Interpreted

Paradigm

Multi-paradigm (event-driven, functional, object-oriented)

Multi-paradigm (object-oriented, procedural, functional)

Multi-paradigm (procedural, object-oriented, generic)

Object-oriented, structured

Memory Management

Automatic (Garbage collection)

Manual

Automatic (Garbage collection)

Syntax

Simple

Complex

Use Cases

Web development, mobile apps, real-time applications

Web development, data analysis, machine learning

System programming, game development, high-performance applications

Large-scale applications, enterprise software

Notable Frameworks/Libraries

React, Angular, Node.js

Django, Flask

Standard Library, Boost

Spring, Hibernate

Community Support

Strong

Job Market

Abundant

List of Companies Using JavaScript

These are some popular companies that use JavaScript in their workflow

Company

Description

Google

Google uses JavaScript extensively in its web services, including Gmail and Google Maps.

Facebook

Facebook’s front-end is built with React, a JavaScript library, for a dynamic user interface.

Netflix

Netflix uses JavaScript for their interactive user interface and in their backend services.

Airbnb

Airbnb relies on JavaScript, using Node.js for scalable back-end development and React for the front end.

LinkedIn

LinkedIn uses JavaScript for both front-end and back-end development, enabling real-time interaction.

Uber

JavaScript is used by Uber for real-time tracking and routing, employing both front-end and back-end technologies.

Twitter

Twitter uses JavaScript for handling its dynamic feeds and providing a seamless user experience.

PayPal

PayPal’s front-end is powered by JavaScript, offering smooth, interactive user experiences.

eBay

eBay uses JavaScript to build their responsive, dynamic web applications and enhance user interactions.

Slack

Slack's web client and several of its real-time communication features are powered by JavaScript.

Career & Jobs in JavaScript

JavaScript opens up a variety of career opportunities, as it is essential for web development, app creation, and dynamic user interfaces. Here are some top career paths for JavaScript developers

Career

Average Salary (INR) Per Annum

Average Salary (USD) Per Annum

JavaScript Developer

₹500,000 – ₹1,200,000

$60,000 – $110,000

Front-End Developer

₹600,000 – ₹1,400,000

$65,000 – $120,000

Full Stack Developer

₹700,000 – ₹1,500,000

$75,000 – $130,000

Back-End Developer

₹600,000 – ₹1,300,000

$70,000 – $125,000

Web Developer

₹500,000 – ₹1,200,000

$55,000 – $100,000

React Developer

₹600,000 – ₹1,300,000

$70,000 – $125,000

Node.js Developer

₹700,000 – ₹1,600,000

$75,000 – $135,000

UX/UI Designer

₹600,000 – ₹1,300,000

$65,000 – $120,000

Software Engineer

₹500,000 – ₹1,500,000

$65,000 – $120,000

If you are a person, who is more into study from Courses. JavaScript Course Provides you Complete Beginner to Advanced learning.

Get detailed list of all JavaScript Topics- JavaScript Complete Guide – A to Z

Introduction of JavaScript First program - Hello Geeks JavaScript Arithmetic Operators JavaScript Type Conversion

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