Userfly Ruined My Weekend – “jQuery(“form.ajax”).ajaxForm is not a function”

I've been a big fan of Userfly because they make usability testing easy. Their tool is really quite amazing. However, this last weekend and into today I've become less of a fan. After a late night deploy last week on a site I've been working on I noticed that none of my javascript worked. Lucky for me Firefox reports the errors. The errors were annoying things like "jQuery("form.ajax").ajaxForm is not a function". I knew for a fact that jquery.form.js was loaded. I could see the code. On occasion I've had problems with the javascript caching that Rails uses - it merges all the files together. I turned that off and it wasn't it

I could only see the error in production. In development everything worked fine. I swore a lot because that is the worst kind of error. yYou feel like you need to debug on the server or setup a staging server. Running my local box in 'production' mode didn't help. I couldn't reproduce the error until I remembered a recent RailsCast about subdomains in Rails 3. He had mentioned a couple of domains you can use that others have kindly set to point at localhost. I used 'http://smackaho.st:3000/'. Sure enough, the javascript errors started showing up which led me to do a bit more searching. I discovered that if you load jQuery and then load it again it will essentially reset your environment. I searched all my code to make sure I wasn't committing this sin and sure enough I wasn't.

The fact that the error only showed up when the domain changed to a production style domain led me to the javascript that we've inserted into the site to make third party services work. I started removing them one at a time and sure enough as soon as I removed userfly everything started working again.

I didn't investigate their code in depth but I'm betting they load jQuery and that it resets the jQuery environment essentially dumping everything I load.

Lesson learned, sort of. These days we rely on third-party services for everything from analytics to usability to comments and the list goes on. It's hard to not use these services as they make your life a lot easier but don't be afraid to throw them aside if you start getting random errors on your site.