javascript - How to receive a ajax callback in ajax post -

i using ajax codeigniter application. i've manged make "ajax checkbox", when click on checkbox, in background specific function called. how make callback, mean know if operation done ok, or maybe problem/error.

my html:

<input type="checkbox" onclick="change_parameter(<?=$dane_leada['lead_id']?>, 'my_parameter');" > 

js:

function change_parameter(lead_id, parametr) {     $.ajax({         type    : "post",     url     : '<?=base_url();?>leads/change_parametr/' + lead_id,         data    : "lead_id=" + lead_id,     data    : "parameter=" + parameter,     });      alert("status changed"); //here should message "ok" or "error"  } 

php in controller:

public function change_parameter($lead_id, $parametr=false)     {          if  ($lead_id != "" , isset($_post['parameter']))                  {             $parameter = $_post['parameter'];                   //odczytujemy zmienną wysłaną przez ajaxa         }          if ($data['dane_leada'][$parameter] == '0') $new_parameter = 1; else $new_parameter = 0;          $dane = array(             'lead_id'   => $lead_id,             $parameter  => $new_parameter,         );          $this->model_leady->mofify_lead($lead_id, $dane);          // return error or confirm     } 

update script this:

function change_parameter(lead_id, parametr) {     $.ajax({         type    : "post",         url     : '<?=base_url();?>leads/change_parametr/' + lead_id,         data    : {lead_id : lead_id,parameter :parameter},         success: function(response){             if(response){                alert("status changed"); //here should message "ok" or "error"             }else{                alert("error :something wrong");             }          },         error: function (err) {           alert("error :something wrong");      });     }); } 

or can add error handler.

error: function (err) {    alert("error :" + err.status); }