What is JavaScript?
JavaScript is a high-level, interpreted scripting language primarily used to add interactivity and dynamic behavior to websites. It is supported by all modern browsers and can also run outside the browser using Node.js.
It’s one of the core technologies of the web, alongside HTML and CSS. HTML gives the structure, CSS gives the styling, and JavaScript brings the page to life with interactive behavior.
Real-Life Analogy: TV Remote
Think of a website like a TV. HTML is the body, CSS is the look, and JavaScript is the remote control that makes things happen. Clicking, scrolling, interacting — all powered by JavaScript.
Why Learn JavaScript?
Here’s what JavaScript allows you to do:
- Add interactivity like dropdowns, sliders, modals, and forms
- Handle user input and browser events (like clicks and keystrokes)
- Communicate with servers using APIs (AJAX/fetch)
- Manipulate webpage content without reloading (DOM manipulation)
- Build full web applications (e.g., Gmail, YouTube frontend)
Where is JavaScript Used?
JS is used in many areas like:
- Web Development (Frontend with React, Vue, Angular)
- Backend Servers (Node.js)
- Mobile Apps (React Native)
- Desktop Apps (Electron.js — like VS Code)
- Browser Games and Visualizations
What Can JavaScript Do in the Browser?
Examples of JavaScript Power:
- Change content dynamically
- Update styles in response to user input
- Show or hide elements
- Validate form data before submission
- Fetch and display live data using APIs
JavaScript + HTML + CSS = Full Website
The 3 Pillars of the Web:
- HTML – Structure (bones)
- CSS – Styling (skin and design)
- JavaScript – Interactivity (muscles and brain)
JavaScript in the Browser vs Server
Initially, JavaScript only ran in the browser. But with Node.js, it now also runs on servers. That means you can build entire applications (frontend + backend) using just JavaScript.
Is JavaScript the same as Java?
Nope! Despite the name, Java and JavaScript are very different languages. Java is compiled and runs on the JVM. JavaScript is interpreted and runs in the browser or with Node.js.
Java vs JavaScript – Key Differences:
- Java is compiled; JavaScript is interpreted
- Java runs on the JVM; JavaScript runs in the browser or Node.js
- Java syntax is similar to C++; JavaScript is more flexible and dynamic
Try This in Your Browser Console
console.log("Hello from jdcodebase!");Bonus: Your First Popup!
alert("Welcome to JavaScript with jdcodebase!");Q: Who created JavaScript and in how many days?
Brendan Eich created JavaScript in just 10 days in 1995 while working at Netscape.
Q: Why is JavaScript named that way?
It was originally called Mocha, then LiveScript. It was renamed to JavaScript for marketing reasons — to ride the popularity of Java at the time.
Modern browsers use engines like V8 (Chrome) or SpiderMonkey (Firefox) to run JavaScript efficiently.