Question

I used this code to maintain scroll position and don’t have a clue of what it means. If someone has the time, can you provide me with an step by step explanation of what it is doing. Here it is:

<script language='javascript'  type='text/javascript'>     var xPos, yPos;     var prm = Sys.WebForms.PageRequestManager.getInstance();          function BeginRequestHandler(sender, args) {          if ($get('<%=lstAuctions.ClientID %>') != null) {              xPos = $get('<%=lstAuctions.ClientID %>').scrollLeft;             yPos = $get('<%=lstAuctions.ClientID %>').scrollTop;         }     }      function EndRequestHandler(sender, args) {          if ($get('<%=lstAuctions.ClientID %>') != null) {              $get('<%=lstAuctions.ClientID %>').scrollLeft = xPos;             $get('<%=lstAuctions.ClientID %>').scrollTop = yPos;         }     }      prm.add_beginRequest(BeginRequestHandler);     prm.add_endRequest(EndRequestHandler);  </script> 

Answer 1

var xPos, yPos; // global variable declaration var prm = Sys.WebForms.PageRequestManager.getInstance(); // Some webforms javascript manager  /* * Begin function with 2 arguments */ function BeginRequestHandler(sender, args) {      // check if the element generated by .net with id 'lstAuctions.ClientID' exists     if ($get('<%=lstAuctions.ClientID %>') != null) {          // get its scroll left and top position and         // assign it to the global variables         xPos = $get('<%=lstAuctions.ClientID %>').scrollLeft;         yPos = $get('<%=lstAuctions.ClientID %>').scrollTop;     } }  /* * this method gets executed last, it uses the  * already set global variables to assign the old scrollpositions again */ function EndRequestHandler(sender, args) {      if ($get('<%=lstAuctions.ClientID %>') != null) {         // assign the previous scroll positions         $get('<%=lstAuctions.ClientID %>').scrollLeft = xPos;         $get('<%=lstAuctions.ClientID %>').scrollTop = yPos;     } }  // first function gets executed on the beginning of a request prm.add_beginRequest(BeginRequestHandler); // second function gets executed on the end of the request prm.add_endRequest(EndRequestHandler);