gistfile1.txt

        this.FbLogin = function(){
         FB.login(function(response) {
          console.log('login response');
          console.log(response);
          if(response.status === 'connected'){
            FB.api('/me/permissions', function(response) {
              console.log(response);
              if(response.data[1].status !== 'granted'){ //email
                retryToLogin();
              }
            });
          }
          // handle the response
         }, {scope: 'public_profile,email', auth_type: 'rerequest'});
        }

        function retryToLogin(){
          alert("We really need your email :s");
          FB.logout(function(response) {
            FB.login(function(response) {
              if(response.status === 'connected'){
                FB.api('/me/permissions', function(response) {
                  console.log(response);
                  if(response.data[1].status !== 'granted'){
                    retryToLogin();
                  }
                });
              }
            }, {
              scope: 'public_profile,email',
              auth_type: 'rerequest'
            });
          });    
        }