parse jason showing undefined error

[karogel]

here's my code:

      function validateLogIn(){
         var url = 'modules/data/get_loginuser.php';
         alert(url);

         $('#fm_login').form('submit',{
            url: url,
            onSubmit: function(){
               return $(this).form('validate');
            },
            success: function(result){
               if (result.errorMsg){
                  $.messager.show({
                     title: 'Error',
                     msg: result.errorMsg
                  });
               } else {
                  alert(result);
                  //result alert is: [{"user_id":"7818","user_name":"karogel","user_password":"827ccb0eea8a706c4c34a16891f84e7b","user_webpass":"827ccb0eea8a706c4c34a16891f84e7b","lastname":"ramiterre","firstname":"rogel","fullname":"rogel ramiterre","nameinitials":"rramiterre","jobtitle":"programmer","admin":"N","branch_name":"Guimba","active":"Y","online":"N","last_active":null,"dateadded":"2015-07-28 07:51:35","addedbyfk":"1","datemodified":"2015-07-28 09:28:47","lastuserfk":"1","is_sync":"0","datetime_sync":"0000-00-00 00:00:00"}]
                  var vfirstname = (result['0'].firstname);
                  alert(vfirstname);
                  $.messager.alert('System Admin','Welcome');                  
//                  $('#dlg_login').dialog('close');      // close the dialog
//                  redirect to main menu
               }
            }
         });      

[stworthy]

Please translate the json string to object before using it.

Code:

success: function(result){
  result = JSON.parse(result);
  //...
}