how to find control inside datalist in javascript

function fnCheckDescription(desc){
                       var lst = document.getElementById('<%=dlService.ClientID%>');
                       for(var i=0;i< lst.rows.length;i++){
                       var elements = lst.rows[i].getElementsByTagName('span');
                           if(elements.length>0){
                                   if(elements[0].innerHTML == desc)
                                   {
                            alert('Matched');
                                               break;
                           }
                   
                   }
            }

http://forums.asp.net/t/1770161.aspx
http://stackoverflow.com/questions/19679928/find-control-inside-datalist-using-javascript