Jquery 在未实现接口 FormData 的对象上调用附加

I'm Trying to upload image on with jquery and ajax. But weird thing happened here. In console Log its showing

TypeError:对未实现的对象调用了"append"

请告诉我我做错了什么？

JS script个

var prosrc=$("#pro_pix img").last().attr("src");
$("#logoform").on('change',function(event){
var postData = new FormData(this);
$("#pro_pix img").last().hide();
$("#pro_pix img").first().show();
event.preventDefault();
$.ajax(
    {
        url : "/function/pro_pic_upload.php",
        type: "POST",
        data : postData,
        success:function(data, textStatus, jqXHR)
        {
        $("#pro_pix img").last().show();
        $("#pro_pix img").first().hide();
        $("#pro_pix h6").text(data);
        },
        error: function(jqXHR, textStatus, errorThrown)
        {
            //if fails     
        }
    });
});

My HTML Markup

 <div class="row">
    <!-- left column -->
    <div id="pro_pix" class="col-md-4 col-sm-6 col-xs-12">
      <div class="text-center">
        <img src="template/image/725.GIF" class="avatar img-circle img-thumbnail" style="display:none" alt="avatar">
        <img src="<?php echo $rowuser['profile_logo']; ?>" class="avatar img-circle img-thumbnail" alt="avatar">
        <h6>Upload a different photo...</h6>
        <form role="form" id="logoform" enctype="multipart/form-data">
        <input id="logo" name="logo" type="file" class="text-center center-block well well-sm">
        </form>
      </div>
    </div>