JS tips

===============add element=================

function AddControl(objId)
{
   var container  = document.getElementById(objId);
   var fIndex=1;
  
   for(var i=0; i<container.childNodes.length; i++)
   {
        if(typeof(container.childNodes[i].id)=="string" && container.childNodes[i].id.substring(0,4) == "file")
          fIndex++;
   }
  
   var newFile = document.createElement("input");
   newFile.setAttribute("type","file");
   newFile.setAttribute("id","file"+fIndex);
   newFile.setAttribute("name","file" + fIndex);
   container.appendChild(newFile);
  
   var newBR = document.createElement("br");
   container.appendChild(newBR);   
}

--window close event---

function DetectBrowserExit()
{
   alert('Execute task which do you want before exit');
}

window.onbeforeunload = function(){ DetectBrowserExit(); }