jquery实现上传文件进度条

<link rel="stylesheet" href="js/bootstrap/bootstrap.min.css" >
<script type="text/javascript" src="js/jquery-3.2.1.min.js"></script>
<script type="text/javascript" src="js/bootstrap/bootstrap.min.js"></script>
<script type="text/javascript" src="js/jquery.form.js"></script>

<form id="uploadfile" action="uploadfile" enctype="multipart/form-data">
 <input type="file" name="file">
 <input type="button" value="上传" id="uplodsss">
 </form>
 <div class="progress">
 <div id="uploadfile_progressbar" class="progress-bar" role="progressbar" aria-valuenow="60" 
 aria-valuemin="0" aria-valuemax="100" style="min-width: 2em;">
 <span id="uploadfile_rate">0%</span>
 </div>
 </div>

<script type="text/javascript">
$(function(){
 $("#uplodsss").click(function(){
 debugger
 $('#uploadfile').ajaxsubmit({
  type:'post', 
  url:"uploadfile", 
  processdata: false, //需设置为false,因为data值是formdata对象，不需要对数据做处理
  contenttype: false, //需设置为false,因为是formdata对象，且已经声明了属性enctype="multipart/form-data"
  resetform: true, //成功提交后，是否重置所有表单元素的值
 uploadprogress: function (event, position, total, percentcomplete) {
 if(percentcomplete > 100){
 percentcomplete = 100;
 }
 var percentval = percentcomplete + '%'; 
 $("#uploadfile_rate").html(percentval); // 文件上传进度显示值
 $("#uploadfile_progressbar").width(percentval); // 进度条状态
 
 }, 
 success:function(data){
 alert("上传文件成功！");
  $("#uploadfile_progressbar").width("0px"); // 进度条状态
  $("#uploadfile_rate").html("0%");
  },
  error:function(){ 
  alert("上传文件失败，请重试！");
  }
 });
 });
})
</script>