Skills101

Online JavaScript compiler (Node.js 20)

Write code, add input, press Run. Free, no sign-up — your code stays in this browser.

JavaScript editor

Output

Press Run to see your program’s output here.

Tips for JavaScript

  • Read all input with require("fs").readFileSync(0, "utf8").
  • console.log prints a line.
  • Runs on Node.js — there is no browser DOM (document, window).
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Frequently asked questions

Is this JavaScript runner free?
Yes. Run JavaScript on Node.js 20 here for free without signing up.
How do I read input in JavaScript?
Use require("fs").readFileSync(0, "utf8") to read everything from the Input box, then split it into lines or words.
Can I use document or alert?
No. The code runs on Node.js (server-side JavaScript), which has no browser page. Use console.log for output.
Can I install npm packages?
No, only built-in Node.js modules are available.