Magento Community Edition 18.104.22.168
Hopefully this will help someone else out there!
I’ve been trying to upload some images through the WYSIWYG editor in Magento for products, but clicking on the “source” image to open the Magento browse/upload window produces an alert window with the following message:
error: error in [unknown object].fireEvent():
event name: open_browser_callback
error message: string is not defined
After chasing this for ages, it turns out the error was a result of the agressive pursuit of speed. The js folder in Magento’s root folder on this site has been minified. That is to say, all the js files have been stripped of comments, white space, etc.
Somewhere in one of those files, an error was introduced which caused the fuss.
Download the same version of Magento you have (22.214.171.124 in my case), and replace the js folder from the download into your Magento installation and come back to minification later on 😉
Note: create a backup of your current js folder, just in case. Delete it once you have confirmed the fix works.