JavaScript Online Runner (JS Playground)

Try out a snippet, check how a built-in method behaves or debug a small function without opening developer tools. Type JavaScript, press Calculate, and see everything it prints with console.log, the value it returns, any error with its line number, and how long it took. The code runs in a separate Web Worker with a time limit, so an endless loop cannot freeze the page.

How to use this tool

1. Type or paste your JavaScript. Top-level await and return work.
2. Set the time limit (1–10 seconds).
3. Press Calculate to run it.
4. Read the console output, return value and any error with its line and column.

Formula

your code → async function in a Web Worker → console messages, return value, errors

console.log, info, warn, error, table, dir, count, time/timeEnd, group and assert are captured. Timers started with setTimeout are waited for (up to the time limit); setInterval keeps running until cleared or stopped. A worker has no document or window, so DOM code will not work here.

Example

The sample adds 19.99 + 5 + 42.5 and prints Total: 67.49, draws a small table of the three prices, waits 200 ms, then prints 0.1 + 0.2 = 0.30000000000000004 — a classic floating-point surprise — and returns { items: 3, total: 67.49 }.