logoJSON Reader

Online JavaScript Compiler

Write, run and debug JavaScript online. This free compiler runs your code on Node.js and streams console output instantly — with stdin input, examples, and share links. No installation or signup.

Loading editor…

Click Run or press ⌘ ↵ to execute your JavaScript code.

Program reads input? .

ReadyLn 1, Col 1

How to use Online JavaScript Compiler

  1. Write or paste JavaScript in the editor, or pick a program from Examples.
  2. If your code reads from process.stdin, type the values in the Input tab.
  3. Click Run or press Ctrl + Enter (⌘ + Enter on Mac).
  4. Read console.log output and errors as they stream into the Output panel.
  5. Click Share for a live link, or download your code as main.js.

Features

Real Node.js runtime

Code runs on Node.js in a secure sandbox — modern ES2023 syntax, async/await, classes and built-in modules like fs and crypto.

Live streaming output

console.log, console.error and console.table output appears as your program runs, with errors highlighted in red.

Standard input

Pass input to your program from the Input tab and read it with process.stdin or fs.readFileSync(0).

VS Code editor

Monaco — the editor behind VS Code — with IntelliSense, auto-format, multi-cursor and bracket matching.

Share in one click

Create a live Code Share link so others can view, edit and run the same code with you.

Autosave

Your code and input are saved in this browser, so nothing is lost when you reload.

What is an online JavaScript compiler?

An online JavaScript compiler lets you execute JavaScript without installing Node.js. You write code in the browser, it runs on a remote Node.js runtime inside a sandbox, and the output is streamed back to you. It is ideal for testing snippets, practising for interviews, learning the language, or sharing a reproducible example with a teammate.

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Frequently Asked Questions

Everything you need to know about JSON Reader

Yes. The JSON Reader online JavaScript compiler is completely free, with no signup and no usage limits.
Your code runs on a current Node.js LTS release, so modern ES2023 features such as optional chaining, top-level classes, async/await and modern array methods all work.
Yes. Type input in the Input tab, then read it with require("fs").readFileSync(0, "utf8") or by listening to process.stdin. Load the “Read input” example to see how.
Node.js built-in modules (fs, path, crypto, util, events and more) are available. Installing third-party npm packages is not supported.
No — the code runs on Node.js, so document and window are not defined. Use your browser’s developer tools for DOM code.
Your code is sent to an isolated sandbox only when you click Run, and it runs with no network access. Share links are created only when you click Share.