JavaScript - Introduction

Overview

Estimated time: 20–30 minutes

JavaScript is the language of the web. It runs in browsers, on servers (Node.js), on the edge, and in native shells. In this track you’ll learn modern, practical JavaScript with complete, runnable examples—focused on browser JavaScript for now.

Learning Objectives

• Describe where JavaScript runs and how it’s delivered to users (inline vs external files).
• Write and run your first script in the browser console and inside a page.
• Know the next steps: enabling JS, script placement, syntax, and your first program.

Prerequisites

• None. This is the first lesson.

Why JavaScript?

• Ubiquitous: every major browser ships a JS engine.
• Event-driven UIs and rich Web APIs (DOM, Fetch, Storage, Workers, Canvas, etc.).
• Mature tooling and ecosystem, with modern language features (ES2015+).

Example

console.log('Hello, JavaScript!');

Expected Output:

Hello, JavaScript!

Common Pitfalls

• Using var instead of block-scoped let/const.
• Confusing == with === (coercion). Prefer strict equality (===).

Checks for Understanding

1. Where does JavaScript execute when you load a web page?
2. What’s the difference between inline scripts and external script files?

Exercises

1. Open DevTools → Console and run console.log('Hello').
2. Create a simple page and add a <script> tag that logs your name.