What is JavaScript?

JavaScript (.js) files contain JavaScript code, the programming language of the web. Created by Brendan Eich in just 10 days in 1995, JavaScript has evolved from a simple scripting language to one of the most widely used programming languages in the world.

JavaScript powers interactive websites, server applications (Node.js), mobile apps, desktop applications, and even IoT devices. It's the only language that runs natively in all web browsers.

Did you know? JavaScript was originally called "Mocha," then "LiveScript," before being renamed JavaScript as a marketing strategy!

History

JavaScript was created by Brendan Eich in 1995 while working at Netscape. What started as a simple scripting language for web pages has become one of the most important programming languages in modern software development.

Key Milestones

  • 1995: Created by Brendan Eich at Netscape in 10 days
  • 1997: ECMAScript standardized (ES1)
  • 2009: Node.js brings JavaScript to the server
  • 2015: ES6/ES2015 major update with classes, modules
  • Present: Annual ECMAScript updates, TypeScript adds types

Key Features

Core Capabilities

  • Universal Browser Support: Runs natively in all web browsers
  • Event-Driven: Asynchronous programming model
  • Dynamic Typing: Flexible type system
  • First-Class Functions: Functions as values
  • Prototypal Inheritance: Unique inheritance model
  • Modern Features: async/await, modules, classes

Common Use Cases

Frontend Development

React, Vue, Angular, Svelte frameworks

Backend Development

Node.js, Express, NestJS servers

Mobile Apps

React Native, Ionic, Capacitor

Desktop Apps

Electron (VS Code, Slack, Discord)

Advantages

  • Universal browser support
  • Full-stack development capability
  • Huge ecosystem and community
  • Fast development with hot reload
  • Asynchronous programming model
  • Easy to learn basics

Disadvantages

  • Weak typing can lead to bugs
  • Browser compatibility issues
  • Callback hell (improved with async/await)
  • Security vulnerabilities if not careful
  • npm dependency complexity
  • Performance limits for CPU-intensive tasks

Technical Information

Format Specifications

Specification Details
File Extension .js, .mjs, .cjs
MIME Type text/javascript
Encoding UTF-8
Paradigm Multi-paradigm
Standard ECMAScript (ECMA-262)
Type System Dynamic, weak typing

Common Tools

  • Runtimes: Node.js, Deno, Bun
  • Package Managers: npm, yarn, pnpm
  • Build Tools: Webpack, Vite, esbuild