Programming language · Since 1995

JavaScript

JavaScript is a dynamic programming language standardized as ECMAScript that runs in every web browser and in runtimes such as Node.js.

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JavaScript was created in 1995 to add behavior to web pages and is now defined by an international standard called ECMAScript. Every major web browser ships with a JavaScript engine, so you can run it without installing anything, and runtimes such as Node.js have made it just as common outside the browser.

Its best-known home is the web front end, where it handles the page and user input. Asynchronous programming built on the event loop, Promises and async/await also makes it a good fit for network-heavy servers and APIs, and the npm ecosystem offers libraries for almost any task. Many languages and tools, TypeScript among them, build on JavaScript.

Open the developer tools console in your browser and you can start experimenting right away. To run programs saved as files, install Node.js. Learn variables, functions, objects and arrays first, then move on to asynchronous code and modules; MDN and javascript.info are excellent places to begin.

Highlights

Runs everywhere

Built into every major browser, and runtimes such as Node.js, Deno and Bun let you use the same language on servers and the command line.

Flexible and dynamic

Variables carry no type declarations and functions are first-class values. A class syntax sits on top of prototype-based objects.

Asynchronous by design

The event loop, Promises and async/await keep programs responsive while they wait on the network or file I/O.

Standard and ecosystem

The TC39 committee revises the ECMAScript standard every year with a strong commitment to backward compatibility, and npm hosts a vast number of packages.

Where it is used

Front ends for websites and web apps
Servers and APIs on Node.js
Desktop apps with Electron and similar tools
Build tools and command-line scripts

Install

1
Install Node.js
Download the LTS installer for your operating system from nodejs.org. On macOS and Linux you can use a version manager such as nvm instead; on Windows, winget works too.
2
Check the installation
Open a new terminal and confirm that the Node.js version is printed. The npm package manager is installed alongside it.
```
node --version
```
3
Create a project
In an empty folder, create a package.json to manage dependencies and scripts.
```
npm init -y
```

Your first program

console.log writes its arguments to standard output (the developer tools console in a browser). Save the code as hello.js and run node hello.js to see Hello, World! printed. You can also paste the same line into a browser console.

hello.js

console.log("Hello, World!");

node hello.js

Everyday tools

npm: The package manager that ships with Node.js; it installs libraries and runs the scripts in package.json.
Visual Studio Code: A code editor with built-in JavaScript IntelliSense and a debugger.
ESLint: A static analysis tool that flags likely bugs and rule violations in your code.
Prettier: A formatter that keeps code style consistent across a whole team automatically.

Step-by-step guide

Six chapters that take you from installation to the core ideas of JavaScript.

Official docs and resources

Frameworks for this language

Discussions

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