javascript进度条实现

<form id="form1" runat="server">
   <asp:ScriptManager ID="scriptManager" runat="server" EnablePageMethods="true" />
   
   <script type="text/javascript">
       var intervalID = 0;
       var progressBar;
       var fileUpload;
       var form;       
       // 进度条      
       function pageLoad(){           
           $addHandler($get('upload'), 'click', onUploadClick);
           progressBar = $find('progress');
       }
       // 注册表单       
       function register(form, fileUpload){            
           this.form = form;
           this.fileUpload = fileUpload;
       }        
       //上传验证
       function onUploadClick() {        
           var vaild = fileUpload.value.length > 0;
           if(vaild){              
               $get('upload').disabled = 'disabled';             
               updateMessage('info', '初始化上传...');                
               //提交上传
               form.submit();                
               // 隐藏frame
               Sys.UI.DomElement.addCssClass($get('uploadFrame'), 'hidden');
               // 0开始显示进度条
               progressBar.set_percentage(0);