使用 input[type=file]上传文件

 var $file = $('#file');
   $('#btn').click(function() {
       var data = new FormData();
       data.append('file', $file[0].files[0]);
       data.append('foo', 'bar'); 

       var xhr = new XMLHttpRequest();
       xhr.open('post', '/upload');
       xhr.onload = function(e) {
           alert(e.currentTarget.response);
       }
       xhr.send(data);
   }); 

   $("#files").change(function(){
       data = new FormData();
       data.append('files', $('#files')[0].files[0]);
       $.ajax({
           type: "post",
           url: "/wap/loanapply/uploadFileUrl",
           processData: false,
           contentType: false,
           data: data,
           success: function(_data){
               _data = JSON.parse(_data);
               if (_data.code == "200") {
                   $scope.$apply(function () {
                      $scope.formData.attachment_ids_url = _data.msg;
                       $scope.up_success = true;
                   });
               } else {
                   $layer.alert(_data.msg, 1000)
               }
           }
       });
   });