Wikipedia:Reporting JavaScript errors

Info to include in bug reports
When you experience an error with gadgets or user scripts and you want to report the issue at the appropriate page, please include the following information: You are urged to have a look at "How to Report Bugs Effectively" by Simon Tatham for hints on how to report bugs effectively, to make sure the issue you are describing can be resolved as promptly as possible.
 * 1) What is the behaviour you're seeing?
 * 2) What is the behaviour you're expecting to see?
 * 3) How can the incorrect behaviour be reproduced? Describe exactly what you're doing and seeing.
 * 4) Confirm that you have tried bypassing your browser cache.
 * 5) Make note of the skin that you use, your browser, browser version, and operating system.
 * 6) Mention relevant JavaScript errors your browser logged. To do that, open your JavaScript console, and copy the relevant error messages. Error messages usually appear in red.

How to open your JavaScript console
Where to find your JavaScript console depends on your browser: On some browsers, you may have to click on the "Console" tab once the developer tools pane opens up.

[*] In Safari, you might have to enable the Develop menu first in Preferences → Advanced → check "Show develop menu in menu bar". For OSX, use Option then hit esc (escape) to open the JavaScript console. Errors will appear in red.

Once you've opened the console...



 * 1) Click on the "Console" tab
 * 2) Scroll to the bottom of the console and look for log entries in yellow and red. Copy or screenshot these.
 * 3) If there is a "triangle" you can press to expand and show more info, do so, and copy/screenshot that info too.

Which one is the error?
Unfortunately there is a lot of junk in the console. Programmers really only need one error message to debug, but the trick is getting the right error message. Here's some examples of useful error messages:


 * Uncaught – typically red
 * Uncaught DOMException
 * Uncaught Error
 * Uncaught ReferenceError
 * Uncaught SyntaxError
 * Uncaught TypeError
 * Uncaught (something in all lowercase)
 * jQuery exception – typically yellow
 * jQuery.Deferred exception