Related to how i use JS helper in CakePHP

i had put following code in my add.ctp file

$alert = $this->Js->alert(‘Hey there’);
echo $alert;

But it simply print that message like

alert(“Hey there”);

it does not give me any alert box like javascript…means what i am not able to use Jshelper…also it doesn’t provide in any error message… I have also included my jquery in default.ctp if any body use Js helper and it works in ur code please give me some idea and i also want to tell u i am new in cakephp…Please help me i had spend 15 days on it but i have no answer yet please suggest any idea to me i wanna to implement ajaxcombo in it…