[jQuery] Re: can't return value after $.ajax call

[Steven Yang]

if thats the case try
function checkIfUsername(o)
{
  var bool;
       $.ajax({
               type: "POST",
               url: ""+CI_ROOT+"index.php/admin/check_if_username",
               data: ({username: username.val()}),
               async: false,
               dataType: "json",
               success: function(data){
                       if(data.bool == true){
                               o.addClass('ui-state-error');
                               updateTips("Your username must be unique");
                               //return false;
   bool = false;
                       }
                       else{
                               //return true;
   bool = true;
                       }
               }
       });
  return bool;
}

i am not very familiar with the case that async:false
but from what you described, this should work