Run Node.js 22 online

What's in Node.js 22

• `--run` flag: execute package.json scripts without npm — faster startup.
• Native fetch, streams and structured clone are all stable.
• V8 12.4 with the Maglev mid-tier optimising JIT enabled by default.

What you get in Node.js 22

Clicking "Run now" opens the playground with this exact code and a matching test case — passes on first Run.

const lines = [];
process.stdin.on('data', d => lines.push(d.toString()));
process.stdin.on('end', () => {
  const n = parseInt(lines.join('').trim());
  console.log(n * 2);
});

How ls-judge runs Node.js 22

Every submission is compiled and executed inside its own Firecracker microVM — the same isolation primitive AWS Lambda uses. No shared container, no shared kernel with other users' code. The Node.js 22toolchain shipped with the microVM is the real thing (not a browser-side emulation): syscalls behave the way they do in production, and the compile / runtime behaviour matches what you would see on your own machine with that version installed.

Feed stdin from the Tests panel, watch verdicts stream per test case over a WebSocket. Free to use, no sign-up, works from any browser.