JSOnline JavaScript Compiler
main.jsPress Run or Ctrl + Enter.
Run JavaScript online and see console.log output straight away — with clear objects, errors and line numbers. Free, and it runs on your device.
How it works
Step 1
Write or paste
Type JavaScript code or paste it in. It is kept on this device for next time.
Step 2
Run
Press Run or Ctrl + Enter. Answers for input go in the Input box.
Step 3
See the output
Output, errors with their line number, and how long it took.
Tips for JavaScript
- console.log shows objects and arrays in full; top-level await works.
- setTimeout and setInterval work — the run ends when every timer is done, or press Stop.
- This is browser JavaScript: require(), fs and process (Node.js) are not available.
Questions
How do I run JavaScript online?
Type or paste your code and press Run (or Ctrl + Enter). Everything you console.log appears in Output.
Does async / await work?
Yes, including await at the top level, promises, setTimeout and setInterval. The run finishes once every timer is done — or press Stop.
Can I use require() or Node.js modules?
No. This is JavaScript as it runs in a browser, so Node.js features such as require(), fs and process are not available.
How do prompt() and alert() work?
prompt() takes the next line from the Input box; alert() prints its message to the output.
Is my code uploaded?
No. It runs in your browser and is saved only on this device.