Asp.net Datalist item fetches using javascript‏

string scr = @"<script>
function Done()
{

var Hdnval;
var HdnControl;
var foo = document.getElementById('dtlImages');
var inps = foo.getElementsByTagName('input');
var inpsmage = foo.getElementsByTagName('img');
for(var i=0;i<inps.length;i++){
if(inps[i].type=='checkbox')
{
if (inps[i].checked== true)
{
HdnControl = inpsmage[i];
Hdnval = inpsmage[i].src;
}
}}
var fName=Hdnval;
var ret= new Array(fName,HdnControl);
//SetPreviewElements(HdnControl,HdnControl)
window.opener.update(ret);
window.close();
}
</script>;";
ClientScript.RegisterClientScriptBlock(this.GetType(), "done", scr);