Verify if at least one checkbox is checked

This snippet verifies if at least one item of list[] is checked

<?php
  var TestCheckbox = document.getElementsByName("list[]");
  var IsChecked = 0 ;
  for (var x = 0 , y = TestCheckbox.length ; x<y ; x++ ){
   if (TestCheckbox[x].checked){
    IsChecked = 1;
   }
  }
  if (IsChecked){
   alert("checked...");
  }else{
   alert("not checked...");
}
?>