jquery ajax Request "unexpected token <"

I generally do not write a blog, do not write bad people do not scold, in this, but also mainly for the record, to meet the same problem of friends to provide a reference.

First of all, I have the functional requirements and environment of this problem: The framework is Mvc5+easyui, the interface is the tabs plugin with Easyui. In the main interface with the Easyui dialog Pop-up window, the same common method, in the main interface call right, in the pop-up page again when the call has been prompted "unexpected token <" This error, on the two requested pictures:

From the picture can be seen, the AJAX request has been successful, and has successfully returned data, but why will still report this mistake, I looked for a long time also can not think why, vaguely think is Easyui plug-in problem, but also can not say what is the problem, Later on a foreign site to see others said to try the original Ajax request, I hold the mentality of trying to try a bit of native Ajax, unexpectedly really successful. To this end, the problem is solved, but the specific root cause I also can not say, you know, we may discuss, but also want to meet the same problem of friends a little help.

jquery ajax Request "unexpected token <"