What is JavaScript?
So far in this series, we've learned about two of the three core technologies used in frontend development.
- HTML creates the structure of a webpage.
- CSS controls how the webpage looks.
But a webpage built with only HTML and CSS is mostly static.
It can display content, but it cannot respond to user actions in meaningful ways.
This is where JavaScript comes in.
JavaScript is the programming language that makes webpages interactive.
It allows websites to respond to user actions, update content, communicate with servers, and perform many other tasks.
What is JavaScript?
JavaScript is one of the most popular programming languages in the world.
It was originally created to make webpages interactive, but today it is used for much more than just websites.
With JavaScript, developers can build:
- Websites
- Web applications
- Backend servers
- Mobile applications
- Desktop applications
- Games
- Browser extensions
- Command-line tools
It is one of the most versatile programming languages available today.
Why Do We Need JavaScript?
Imagine visiting an online shopping website.
When you:
- Click a button
- Search for a product
- Add an item to your cart
- Fill out a form
- Open a navigation menu
- Watch content update without refreshing the page
JavaScript is usually responsible for making these interactions possible.
Without JavaScript, websites would be much less interactive.
What Can JavaScript Do?
JavaScript can perform many different tasks, including:
- Responding to button clicks
- Validating forms
- Showing or hiding content
- Updating parts of a webpage
- Creating animations
- Building image sliders
- Playing games
- Making API requests
- Displaying notifications
- Communicating with backend servers
These features make websites feel dynamic and responsive.
JavaScript is a Programming Language
Unlike HTML and CSS, JavaScript is a programming language.
This means it includes programming concepts such as:
- Variables
- Functions
- Conditions
- Loops
- Objects
- Arrays
- Classes
These features allow developers to write logic that controls how applications behave.
How Does JavaScript Work with HTML and CSS?
The three core frontend technologies each have a different responsibility.
HTML provides the structure.
CSS controls the appearance.
JavaScript adds behavior and interactivity.
Together, they create modern webpages that are both attractive and functional.
Modern JavaScript
JavaScript has evolved significantly over the years.
Modern JavaScript includes many powerful features that make development easier and applications more efficient.
Today, developers use JavaScript to build everything from simple websites to large enterprise applications.
Because of its popularity, a huge ecosystem has grown around JavaScript.
JavaScript Libraries
As web applications became larger, developers created libraries to simplify common tasks.
A library is a collection of reusable code that helps developers build applications more efficiently.
Some popular JavaScript libraries include:
- React
- jQuery
- D3.js
- Three.js
Each library focuses on solving different kinds of problems.
For example, React is widely used for building user interfaces.
JavaScript Frameworks
Developers also use frameworks that provide a complete structure for building applications.
Frameworks help organize projects and include features that simplify development.
Some popular JavaScript frameworks include:
Frontend Frameworks
- Angular
- Vue
- Svelte
Full-Stack and Backend Frameworks
- Next.js
- Nuxt
- Express.js
- NestJS
These frameworks help developers build applications more efficiently without starting from scratch.
JavaScript Beyond the Browser
Many beginners think JavaScript only runs inside a web browser.
That is no longer true.
Today, JavaScript can also run on servers using technologies like Node.js.
This allows developers to use JavaScript for backend development as well.
Because of this, one programming language can be used to build both the frontend and the backend of an application.
This is one of the main reasons JavaScript has become so popular.
Is JavaScript Still Used Today?
Absolutely.
JavaScript is one of the most widely used programming languages in the software industry.
It powers millions of websites and applications around the world.
Whether you're using:
- YouTube
- Amazon
- Netflix
- Gmail
JavaScript is helping power many of the interactive features you use every day.
Summary
JavaScript is a programming language that adds interactivity and behavior to webpages.
While HTML creates the structure and CSS controls the appearance, JavaScript allows websites to respond to user actions, update content, communicate with servers, and perform complex tasks.
Today, JavaScript is used not only for frontend development but also for backend development, mobile applications, desktop applications, games, and many other types of software.
It has a rich ecosystem of libraries and frameworks that make it one of the most powerful and widely used programming languages in modern software development.
Learn more:
This article introduces the basics of JavaScript. If you'd like to learn JavaScript in depthâfrom variables and functions to objects, asynchronous programming, the DOM, APIs, ES6+, and modern development practicesâexplore our complete JavaScript tutorial series.