Validation of Checkbox in Listview Control by Jquery/Javascript? -

i trying validate checkbox 1 of item in listview control. have button check define clientclick function on button , wrote javascript code. didn't work. displaye lstviewtest object null..

function btnclick() {     var listview = document.getelementbyid('<%= lstviewtest.findcontrol("tableitem").clientid %>');       (var = 0; < listview.rows.length; i++) {         var inputs = listview.rows[i].getelementsbytagname('input');         (var j = 0; j < inputs.length; j++) {             if (inputs[j].type == "checkbox" || inputs[j].type == "checkboxsend")                 if (inputs[j].checked)                 return true;         }         alert("please select @ least one");         return false;     }  } 

thanks in advance, appreciate time