Technology

JavaScript

The main language of the web – runs in the browser and on the server (Node.js). Foundation for React, Angular, Vue.js and Next.js.

JavaScript is the most widely used programming language and the only one that runs natively in every major browser. What started as a simple scripting language for form validation is now a full ecosystem for frontend (React, Vue, Angular), backend (Node.js, Deno, Bun), mobile (React Native), desktop (Electron) and even ML (TensorFlow.js). TypeScript – a typed superset of JavaScript – is the standard for serious projects.

What is JavaScript?

JavaScript is a dynamically typed, interpreted language created in 1995 by Brendan Eich at Netscape. It is multi-paradigm: object-oriented, functional and event-driven. In the browser it manipulates the DOM, handles user events and talks to APIs. Node.js (since 2009) runs JavaScript on the server. The language is standardized by ECMAScript (TC39) with yearly updates (ES2015 was a major step). Modern features include arrow functions, async/await, destructuring, modules (import/export), classes, promises, optional chaining and nullish coalescing.

How does JavaScript work?

JavaScript runs in the browser or a runtime (Node.js, Deno, Bun). The V8 engine (Chrome, Node.js) JIT-compiles it to machine code for speed. In the browser it accesses the DOM, handles events, performs fetch() and updates the page. On the server, Node.js uses a single-threaded event loop and non-blocking I/O for many concurrent connections. Package managers (npm, yarn, pnpm) manage over 2 million packages on npm.

Practical Examples

React SPA: Single-page app with React – UI, state and API calls in JavaScript/TypeScript.

Node.js API: Express/Fastify backend serving REST/GraphQL, Prisma on PostgreSQL, JWT auth.

Next.js full-stack: SSR, API routes and database in one TypeScript project.

Electron desktop: VS Code, Slack and Discord are built with JavaScript/TypeScript and Electron.

Typical Use Cases

Frontend: Interactive sites and web apps with React, Vue or Angular

Backend: APIs and server logic with Node.js, Express, Fastify or NestJS

Full-stack: One language (TypeScript) from frontend to database

Mobile: Cross-platform with React Native or Ionic/Capacitor

Tooling: Build (Vite, Webpack), lint (ESLint), format (Prettier), test (Jest, Vitest)

Advantages and Disadvantages

Advantages

Universal: Browser, server, mobile and IoT
Huge ecosystem: Over 2 million npm packages
TypeScript: Types and tooling make it suitable for large codebases
Full-stack: One language reduces context switching
Community: Huge amount of tutorials, courses and Q&A

Disadvantages

Dynamic typing: Without TypeScript, type errors appear at runtime
Framework overload: Many frameworks and libraries can be overwhelming
Supply chain: Malicious or vulnerable npm packages are a real risk
Performance: For heavy CPU (e.g. image processing, ML training) C++, Rust or Python can be better
Single-thread: Node.js needs specific patterns for CPU-bound work (worker threads)

Frequently Asked Questions about JavaScript

JavaScript or TypeScript?

TypeScript is the default for professional projects. It adds static types, interfaces and enums. Benefits: catch errors at compile time, better IDE support and refactoring, easier maintenance of large codebases. Learning curve is small if you know JavaScript. Recommendation: use TypeScript for new projects.

Is JavaScript hard to learn?

Basics (variables, functions, loops, DOM) can be learned in a few weeks. Complexity is in async (promises, async/await), the ecosystem (which framework, which bundler?) and advanced topics (closures, prototypes, event loop). Easy to start, hard to master.

Node.js or Deno/Bun?

Node.js is the established choice: largest community and package set. Deno (by Node’s creator) is TypeScript-first, more secure (explicit permissions) and uses web-standard APIs. Bun is the fastest runtime and includes bundler and test runner. For production we’d choose Node.js; Bun is an increasingly attractive option for new projects.

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