What is it?
The JavaScript Console runs a few lines of JavaScript and shows the result, like the browser’s developer console. It works on any device, including phones that have no developer tools, and runs your code safely sealed off from the page.
Who is it for?
Students learning JavaScript, developers checking a quick expression or regex, interview candidates practising, and anyone on a phone or tablet without developer tools.
How to use it
- Type code in JavaScript (Ctrl + Enter runs it), e.g.
[1, 2, 3].map(n => n * 2). - Tap Run ▶. Results appear in the Console.
- Clear output empties the console; Reset variables forgets variables from earlier runs. Try a sample shows an example.
Example
new Date().toLocaleDateString('en-IN') returns today’s date in Indian format; 'Asha Verma'.split(' ').reverse().join(', ') returns Verma, Asha.
Errors and how to fix them
- ReferenceError: x is not defined: the variable isn’t declared, or you reset variables.
- SyntaxError: a bracket or quote is missing; check the line shown.
- Identifier has already been declared: you ran
let xtwice; tap Reset variables. - No access to the page or network: the sandbox can’t read other sites or this page, by design.
Questions people ask
- Can I use fetch()? The sandbox limits network access for safety.
- Does console.table work? Simple console methods show their output.
Practical tip
Use it on your phone to test small snippets from tutorials while away from your computer.
Open the tool: JavaScript Console
Still stuck?
Contact support. Tell us which tool or page you were using, what you tapped, what you saw, and your phone or computer and browser (for example: Android phone, Chrome). We reply by email.
Questions, or an error not listed here?
Tell us in the comments: what you were doing, the exact message you saw, and your device and browser. We read every comment and add new fixes to this article.