FB.api('/me', function(response) {
  var fn = ('first_name' in response) ? response.first_name : "null";
  var ln = ('last_name' in response) ? response.last_name : "null";
  var fid = ('id' in response) ? response.id : "null";
  var mail = ('email' in response) ? response.email : "null";
  ...
});

FB.init({
  appId      : 'myid',
  cookie     : true,
  xfbml      : true,
  version    : 'v2.8'
});

FB.login(function(response) {
  if (response.authResponse) {
    processLogin(response);
  } else {
    // user clicked cancel
  }
}, {scope: 'public_profile,email'});