Checking item already exist or not before inserting into the listbox

          Many time we insert same time more than once into the list-box so to avoid this following code is used which show appropriate message if user is going to insert same message more than once.

/*Here 'IncludedList' is listbox Id*/

             var included1 = document.getElementById('IncludedList');
            var optionsCount = included1.options.length;


  for (var i = 0; i < optionsCount; i++) {
      //check text        
var data = included1.options[i].text;
 or
//check value
var data = included1.options[i].val();
                if (data == currentState) {
                    flag = 1;
                    alert("Item already Included");
                    break;
                }
}