NodeJS 22.19.0

Online JavaScript Editor & Code Runner

Name: myCompiler JavaScript
Author: myCompiler

myCompiler is a free online JavaScript editor and code runner that lets you write, run, and share JavaScript code directly in your browser. It works as your JavaScript playground, sandbox, fiddle, cloud compiler, and online REPL. No downloads, no installation needed. Just open the editor and start coding with syntax highlighting, autocomplete, and instant output.

Start coding in JavaScript How it works

27+ languages Used by 1M+ developers Free forever

main.js

const users = [
  { name: "Alice", age: 25 },
  { name: "Bob", age: 30 },
  { name: "Charlie", age: 35 }
];

const adults = users.filter(u => u.age >= 30);
for (const u of adults) {
  console.log(`${u.name}: ${u.age}`);
}

Output

Bob: 30 Charlie: 35

How to run JavaScript code online

Three steps to go from idea to running JavaScript code in this online playground. No account required.

Write your code

Open the JavaScript editor and start writing. The smart editor gives you syntax highlighting, autocomplete, and error detection as you type.

Click Run

Hit the Run button or press +Enter to run your JavaScript code on secure, sandboxed cloud servers.

See results

Output appears instantly in the integrated terminal. Errors and exceptions show up with clear, helpful messages.

Everything you need to code in JavaScript

A complete online JavaScript IDE and coding playground in your browser. Write, run, and share code without any setup.

Zero setup required

Start coding in seconds with this browser-based JavaScript interpreter. No downloads, no installations, no environment configuration. Open your browser, go to myCompiler, and start writing JavaScript code immediately.

Works on any device with a web browser. Desktop, laptop, tablet, phone, Chromebook. There is nothing to install and nothing to configure.

Feature-rich code editor

Write JavaScript with a professional-grade code editor built into your browser. Syntax highlighting colors your code for readability, making keywords, strings, and functions easy to distinguish at a glance.

Intelligent autocomplete suggests methods and properties as you type, and real-time error detection catches mistakes before you run your code.

Multi-file projects

Create and manage multiple files in a single project. Use the file sidebar to organize your code into modules, then import them across files just like in a desktop IDE.

Build modular applications with proper project structure. Each file is editable, and you can switch between them instantly.

Run code instantly

Click the Run button or press +Enter to execute your JavaScript code instantly. This online code runner displays output immediately in the integrated terminal panel. Your code runs on secure, sandboxed cloud servers and results appear in seconds.

Error messages and tracebacks are displayed clearly, making it easy to find and fix issues. The terminal supports ANSI colors for rich output formatting.

Ready to try it? Write and run your first JavaScript program in seconds.

Open JavaScript editor

JavaScript on myCompiler

myCompiler runs NodeJS 22.19.0, always up to date with the latest stable release. You get a full browser-based IDE with syntax highlighting, intelligent code completion, multi-file project support, a built-in terminal for real-time output, and standard input (stdin) for interactive programs. Write, compile, run, and debug JavaScript code on any device. Desktop, laptop, tablet, phone, Chromebook. Zero downloads, zero configuration, and no sign-up required. Save your programs with a unique URL and share them with anyone. You can also embed a working JavaScript editor on your own website.

Use this online JavaScript playground as a quick code executor for testing snippets, a coding sandbox for learning, or a cloud compiler for coding interview preparation. The editor includes dark mode for comfortable coding, keyboard shortcuts for faster workflows, and clear error messages with line numbers so you can debug quickly. Students use it for homework and practice. Teachers use it to share working examples. Developers use it to prototype ideas. myCompiler is beginner-friendly, fast, and completely free. It works in any modern web browser.

Start coding in JavaScript

JavaScript code examples

Common JavaScript patterns you can try in the online compiler. Each example is ready to run.

Hello World in JavaScript

main.js

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

Variables and Data Types in JavaScript

main.js

const name = "Alice";
let age = 30;
const isStudent = true;
console.log(`${name} is ${age} years old`);

If-Else Conditionals in JavaScript

main.js

const x = 10;
if (x > 0) {
  console.log("Positive");
} else if (x === 0) {
  console.log("Zero");
} else {
  console.log("Negative");
}

For and While Loops in JavaScript

main.js

for (let i = 0; i < 5; i++) {
  console.log(`Count: ${i}`);
}

const fruits = ["apple", "banana", "cherry"];
for (const fruit of fruits) {
  console.log(fruit);
}

Functions in JavaScript

main.js

function greet(name, greeting = "Hello") {
  return `${greeting}, ${name}!`;
}

console.log(greet("Alice"));
console.log(greet("Bob", "Hi"));

Arrays and Collections in JavaScript

main.js

const fruits = ["apple", "banana", "cherry"];
fruits.push("date");
console.log(fruits[1]);

const person = { name: "Alice", age: 30 };
console.log(person.name);

Classes and Objects in JavaScript

main.js

class Dog {
  constructor(name, breed) {
    this.name = name;
    this.breed = breed;
  }

  bark() {
    return `${this.name} says Woof!`;
  }
}

const dog = new Dog("Rex", "Labrador");
console.log(dog.bark());

Error Handling in JavaScript

main.js

try {
  const result = JSON.parse("invalid json");
} catch (e) {
  console.log(`Error: ${e.message}`);
} finally {
  console.log("Done");
}

File I/O in JavaScript

main.js

const fs = require("fs");

// Write to file
fs.writeFileSync("output.txt", "Hello, File!");

// Read from file
const content = fs.readFileSync("output.txt", "utf8");
console.log(content);

Async/Await in JavaScript

main.js

function delay(ms) {
  return new Promise(resolve => setTimeout(resolve, ms));
}

async function main() {
  console.log("Start");
  await delay(100);
  console.log("Done after 100ms");
}

main();

Try these examples in the editor

How to take input in JavaScript online

myCompiler supports standard input (stdin) for JavaScript programs. Use JavaScript's standard input functions to read user input. Enter your input data in the stdin panel before running your program.

This works for both single-line and multi-line input. You can read strings and convert to numbers using the language's built-in I/O functions.

Try it yourself

main.js stdin supported

const readline = require("readline");
const rl = readline.createInterface({
  input: process.stdin
});

const lines = [];
rl.on("line", (line) => lines.push(line));
rl.on("close", () => {
  console.log(`Hello ${lines[0]}!`);
  console.log(`You'll be ${+lines[1] + 1} next year.`);
});

stdin

Alice
25

Output

Hello Alice!
You'll be 26 next year.

No setup, no sign-up. Start writing JavaScript code right now.

Start coding now

Getting started with JavaScript online

You can start writing and running JavaScript code right now without installing anything. Type your code, and click Run. This free JavaScript code runner executes your program instantly and displays the output in the terminal panel below the editor. Open the JavaScript online editor, type your code, and click Run.

If you're new to JavaScript, use this online JavaScript playground to start with the basics like variables, data types, conditionals, and loops. The code examples above cover all the fundamentals you need to get started. Each example can be copied into the sandbox and run immediately. No setup, no configuration.

As you progress, try creating multi-file projects, using libraries, and sharing your programs with others via URL. Sign up for a free account to save your work and build a personal library of programs. myCompiler works as a full online JavaScript IDE right in your browser.

Who uses myCompiler

Whether you're learning to code, preparing for interviews, or prototyping ideas, myCompiler is built for you.

Students & Learners

Practice exercises, complete homework assignments, and experiment with code without installing anything on school or personal computers.

Teachers & Educators

Share code examples with students via unique URLs. Embed the compiler in course materials so students can run examples directly in the browser.

Interview Candidates

Practice coding interview problems, test algorithms, and verify solutions quickly during preparation for technical interviews.

Professional Developers

Quickly prototype ideas, test code snippets, or try out a library without setting up a local environment. Great for quick experiments.

Content Creators & Bloggers

Embed interactive examples in blog posts, tutorials, and documentation so readers can run code without leaving the page.

Teams & Collaborators

Share code snippets with colleagues via URLs. Others can view, run, and fork your code to build on your work.

myCompiler vs. local IDE

Why use an online JavaScript compiler instead of installing one locally?

Feature	myCompiler	Local IDE
Setup time	Instant	Minutes to hours
Installation	None required	JavaScript + IDE required
Device support	Any browser	Desktop only
Sharing code	One-click URL	Manual (file, git, etc.)
Languages	27+ in one place	One at a time
Cost	Free forever	Free to $$$
Works on Chromebook	Yes	Limited

What is JavaScript?

JavaScript is the world's most widely used programming language, running in every web browser on the planet and on servers via Node.js and Deno. Originally created by Brendan Eich in just 10 days in 1995 for Netscape, JavaScript has grown into a full-featured language that powers everything from simple web pages to large-scale applications at companies like Google, Facebook, and Netflix.

Modern JavaScript (ES6+) includes features like arrow functions, async/await, destructuring, modules, and classes, making it far more expressive than its early incarnations. It is the only programming language that runs natively in web browsers, making it indispensable for frontend web development.

What is JavaScript used for?

JavaScript is used for frontend web development with frameworks like React, Vue, and Angular, backend development with Node.js and Express, mobile apps via React Native, desktop applications with Electron, serverless functions, and game development using Phaser and Three.js. No other language spans as many platforms and use cases.

JavaScript for beginners

JavaScript is often the first language beginners learn because it works immediately in any web browser, open the browser console and start coding. Its forgiving syntax, dynamic typing, and instant visual feedback make it approachable. Use myCompiler's online JavaScript editor to practice algorithms, data structures, and ES6+ features without any setup. A simple console.log("Hello, World!") is all it takes to get started.

JavaScript vs other languages

Compared to Python, JavaScript has a more complex syntax but runs in browsers natively, making it essential for web development. Compared to TypeScript, JavaScript requires no compilation step but lacks static type checking, which can make large codebases harder to maintain. Compared to Java, JavaScript is dynamically typed, more flexible, and much more concise for web tasks, but lacks Java's strict structure for large enterprise applications.

Why use an online JavaScript compiler?

An online JavaScript editor, also known as a JavaScript playground, fiddle, or sandbox, lets you write and run JavaScript code instantly in your browser without installing Node.js. It is perfect for testing ES6+ features, experimenting with algorithms, practicing for coding interviews, and sharing code snippets with others via a simple URL.

myCompiler's online JavaScript IDE runs on Node.js, supporting modern ES modules, async/await, Promise, and the full Node.js standard library. Save and share programs, add stdin input, or embed your examples in tutorials, all free with no sign-up required.

Why is JavaScript so popular?

JavaScript's dominance comes from being the only language that runs natively in web browsers, meaning any web developer must know it. Its versatility, from frontend to backend to mobile, means one language can power an entire product. The enormous npm ecosystem (over 2 million packages), active community, and constant evolution through the ECMAScript standard have kept JavaScript at the top of popularity rankings for over a decade.

JavaScript career opportunities

JavaScript skills open doors to frontend developer, full-stack developer, React/Vue/Angular developer, Node.js backend engineer, and mobile developer roles. JavaScript consistently ranks as the most in-demand programming language in job postings. Whether you specialize in frontend, backend, or full-stack, JavaScript proficiency is a foundational career asset in tech.

Try JavaScript online Free · No sign-up needed

Keyboard shortcuts

Code faster with these keyboard shortcuts in the myCompiler editor.

Run code

+ Enter

Save program

+ S

Toggle comment

+ /

Indent line

Tab

Unindent line

Shift + Tab

Undo

+ Z

Select next occurrence

+ D

Find & replace

+ H

Embed the JavaScript compiler on your website

Add an interactive JavaScript compiler to your website, blog, or learning platform. Readers can write and run JavaScript code directly on your page without leaving it.

Perfect for technical tutorials, coding courses, documentation, and educational content. Save a program on myCompiler and use the embed link to add it to any webpage.

Embedded JavaScript editor and code runner

HTML

<iframe
src="https://www.mycompiler.io
    /embed/nodejs"
width="100%"
height="400"
frameborder="0">
</iframe>

Why developers choose myCompiler

A full-featured online IDE for JavaScript and 27+ other programming languages.

27+ Languages

Python, JavaScript, Java, C++, Rust, Go, TypeScript, C#, and many more. All compilers and interpreters in one place. Switch languages instantly.

Dark & Light Mode

Switch between light and dark themes with one click. Code comfortably in any lighting condition, day or night.

Mobile Friendly

Fully responsive editor optimized for phones, tablets, and Chromebooks. Code on any device with a web browser. No app download needed.

Save & Share Code

Save programs to your account, share via unique URLs, and let others view, fork, and run your code. Great for collaboration and code reviews.

Tags & Organization

Organize your saved programs with tags and find them quickly with search and filters. Build a personal library of code snippets and solutions.

No Account Required

Start writing and running code immediately. No sign-up, no email, no credit card. Create a free account later only if you want to save your work.

Explore more programming languages

myCompiler supports 27+ languages. Switch between them anytime. All free, all in one place.

Deno

Python

Ruby

View all 27+ languages

Frequently asked questions

Common questions about using the online JavaScript compiler, playground, and code runner.

Yes! myCompiler is completely free for all supported languages including JavaScript. There are no subscriptions, no premium tiers, and no hidden costs. Every feature is available at no charge.

myCompiler keeps its JavaScript environment up to date. You can see the exact version on the language details section of this page. We regularly update all language runtimes to their latest stable versions.

myCompiler runs JavaScript using a server-side Node.js runtime, so browser APIs like the DOM are not available. You can run standard JavaScript code including ES modules, async/await, and most Node.js built-in modules.

Simply open the JavaScript editor, write or paste your code, and click the Run button. Your code will be executed on our servers and the output will appear in the terminal panel within seconds.

Yes. Click Save to store your program. You will receive a unique URL that you can share with anyone. Recipients can view, fork, and run your code.

Yes. myCompiler supports multi-file projects. You can create, rename, and delete files in the sidebar. This lets you organize your JavaScript code just like in a local IDE.

Yes. All code runs in isolated containers on our servers. Each execution gets its own sandboxed environment that is destroyed after completion. Your code cannot affect other users or our infrastructure.

Yes. myCompiler has a responsive design optimized for phones and tablets. You can write and run JavaScript code on the go. The mobile interface uses tabs for switching between the editor, output, and file panels.

Yes. Click the Input tab in the bottom panel, type or paste your input data, then click Run. Your program will read from the input you provided.

Execution is fast. Code runs on our optimized cloud infrastructure and output typically appears within seconds. Execution time depends on the complexity of your program.

Yes. myCompiler provides an embed feature. You can copy an iframe snippet and paste it into your website, blog, or documentation. Visitors can edit and run code directly on your page.

myCompiler supports common editor shortcuts including Run (Ctrl/Cmd+Enter), Save (Ctrl/Cmd+S), Find (Ctrl/Cmd+F), and more. See the keyboard shortcuts section on this page for the full list.

No. myCompiler requires an internet connection because code is compiled and executed on our cloud servers. The editor itself loads in your browser, but running code requires connectivity.

myCompiler offers a fast, free, zero-setup environment with a modern code editor, multi-file support, dark mode, and instant sharing. It is ideal for learning, prototyping, interviews, and sharing code examples.

Yes. myCompiler is great for practicing algorithms and coding problems. You can write JavaScript code, provide custom input, and test your solutions instantly. Save your work and come back to it anytime.

Use print statements or console output to trace your program's behavior. myCompiler shows all standard output and error messages in the terminal panel. Error messages include line numbers to help you locate issues.

Ready to write JavaScript code?

Open the free JavaScript playground and start coding immediately. No downloads, no account required.

Start coding in JavaScript

Free · No sign-up required · NodeJS 22.19.0