Run Deno online

Deno is Ryan Dahl's post-Node take on a JavaScript/TypeScript runtime: TypeScript native, ES modules first, permissions system by default, standard library that ships with the runtime.

ls-judge runs Deno 2 inside a Firecracker microVM. No `--allow-net` flags matter here — the sandbox blocks network anyway. Bring code, get verdicts.

What you get in Deno

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

const lines=[];
process.stdin.on('data',d=>lines.push(d));
process.stdin.on('end',()=>{
  const n=parseInt(lines.join('').trim());
  process.stdout.write((n*2)+'\n');
});

Common questions about Deno on ls-judge

Which Deno?

Deno 2 (the current major).

TypeScript out of the box?

Yes — Deno runs .ts files natively, no tsc step.

jsr / npm imports?

No network in the sandbox. Bring bundled source.

Free?

Yes.

• Deno manual↗