ajax post to laravel can't redirect,form submit can redirect

First of all, I am a Chinese student,I will try my best to explain my question,but my English not very good.So,sorry. In my login web ,I use ajax post data(id,passwd...) to a route.after all confirm,if the data was right,login web direct to another web.but the controller function can not redirect .

return redirect('wx/setdev'); //not work in controller function ,but work in route function

If I submit a form to controller .controller can redirect the web.but ajax can't.

$.post("",{

                    _token : "",
                    user : $('#num').val(),
                    passwd : $('#passwd').val()
                });

I don not know why. Thanks

via 杨苏杭