django不能通过ajax发起请求返回JSON？ 400 请求出错 

这是后台处理的

def checkemail(request):

    return HttpResponse(result, mimetype='application/javascript')

这是AJAX部分

if(valid_email($('#reg-for-email').val())){
            var email = $('#reg-for-email').val();
            //这里把用户输入的EMAIL地址提交到后台数据库中去验证是否已存在。
            $.ajax({
               type:"POST" ,
               url:"/reg/checkemail",
               data:"email=" + email ,
               cache: false,
               success: function(result){
                   if (result==1)
                     {
                       $("#reg-for-email-msg").removeClass("g-hide");
                       $('#reg-for-email-msg').removeClass("msg-isok").addClass("msg-error").html("该邮箱已存在！");
                       eok = true;
                     }
                     else
                     {
                       $("#reg-for-email-msg").addClass("g-hide");
                       eok = false;
                     }

               }
             })

        }

URL的配置是:

 url(r'^reg/checkemail/', 'reg.views.checkemail', name='ce'),