Introduction

Why JavaScript?

JavaScript is the language of the web. It runs in every browser, powers millions of websites and apps, and is consistently one of the most popular programming languages in the world.

  • Everywhere -- Every browser runs JavaScript natively. No install, no compile step, no runtime to set up. Open the console and start coding.
  • Full-stack -- With Node.js, JavaScript runs on servers too. One language for frontend, backend, scripting, and tooling.
  • Huge ecosystem -- npm hosts over 2 million packages. Whatever you need to build, there is probably a library for it.
  • Fast enough -- Modern JavaScript engines (V8, SpiderMonkey) use JIT compilation. JavaScript is fast enough for games, real-time apps, and data processing.
  • Expressive -- First-class functions, closures, destructuring, and the rest of the modern ES6+ syntax make JavaScript surprisingly elegant.

The Story

JavaScript was created by Brendan Eich in just 10 days in May 1995 while working at Netscape. Originally called Mocha, then LiveScript, it was renamed JavaScript as a marketing move to capitalize on Java's popularity — despite having almost nothing to do with Java.

The language was standardized in 1997 as ECMAScript (ES1). For years, browser incompatibilities made JavaScript painful to write. The release of ES6 (ES2015) transformed the language: let, const, arrow functions, classes, modules, Promises, and much more arrived all at once.

Today, JavaScript evolves yearly, with new features added through TC39, the standards committee. Engines like Google's V8 (used in Chrome and Node.js) make it one of the fastest dynamic languages in existence.

Who Uses JavaScript

Practically everyone in web development:

  • React, Vue, Angular -- the dominant frontend frameworks are all JavaScript.
  • Node.js -- JavaScript on the server, powering Netflix, LinkedIn, and Uber.
  • Electron -- VS Code, Slack, and Figma are built with JavaScript.
  • React Native -- mobile apps from a single JavaScript codebase.

What You Will Learn

This course contains 15 lessons organized into 5 chapters:

  1. Basics -- console.log, variables with let and const, and string operations.
  2. Control Flow -- Conditionals with if/else, for loops, and while loops.
  3. Functions -- Declaring functions, arrow functions, and closures.
  4. Arrays -- Creating and modifying arrays, then map, filter, and reduce.
  5. Objects -- Key-value pairs, property access, and destructuring.

Each lesson explains a concept, shows examples, and gives you an exercise to write and run in your browser.

Let's get started.

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