JavaScript Powers the Modern Web
JavaScript Introduction
An introduction to JavaScript — what it is, where it runs, and what you can build with it.
What you'll learn
- Understand what JavaScript is and why it matters
- Run your first line of JavaScript
- Know what you can build with it
JavaScript is the programming language of the web. It runs in every browser, on every device that opens a web page. If you’ve ever seen a website do something after you clicked — show a menu, validate a form, load more content — that was JavaScript.
What You’ll Learn
By the end of this track, you’ll be able to read, write, and debug real-world JavaScript. You’ll be comfortable with the modern syntax (ES2024), the DOM, async code, and the platform APIs every web developer uses every day.
A Tiny Taste
This is a real, working JavaScript program. It logs a message to the browser’s developer console.
console.log("Hello, world!");Don’t worry about every character yet — you’ll learn what console.log
means in the next few lessons. The important thing is: this code runs.
Click Try it Yourself, change "Hello, world!" to your name, and
press Run to see the output update.
Where Does JavaScript Run?
Originally, JavaScript only ran in web browsers. Today it runs almost everywhere:
- In every browser — the web is built on it.
- On servers — via Node.js, Deno, and Bun.
- In mobile apps — via React Native and similar.
- On the desktop — via Electron (VS Code, Slack, Discord).
- In databases — MongoDB lets you query in JavaScript.
- In AI tools and CLIs — most modern devtools speak JavaScript.
What You’ll Need
Nothing. Every lesson in this track runs in your browser. You don’t need to install a thing.
When you’re ready to write your own programs locally, all you’ll need is a text editor (we recommend VS Code) and a modern browser (you already have one).
Up Next
You’ll learn the two ways to add JavaScript to a web page.
JavaScript Where To →