Not sure why upload plugin isnt working

Not sure why upload plugin isnt working

I'm building a small database application with CodeIgniter and some bootstrap and jquery plugins. I'm working on an uploader tool by implementing a jquery upload plugin so that users can upload attachments to a folder on the server. Right now uploads are supposed to just be going to a folder named "upload" in the public root folder of the wamp server. Once I get these errors worked out I will make it so that they go into folders named after the partID - so the upload app doesnt need to interact with the actual MySQL database.

It shows an error each time I try to upload though, I'm pretty new to jquery though and dont know much about json so I'm not sure whats going on. Any help would be much appreicated. You can see my app here

and the plugin I'm trying to implement is here

Thanks