Question

In my application I have a function like this one:

getProfile = function() {
  FB.api('/me', function(response) {
    console.log(response);
  });
  return false;
};

Which requests the “me” object from the Facebook Graph API over JavaScript, and it works as expected when I attach it to the onClick event of a regular link or call it from the console directly, but when I try to call it from the Facebook log in button:

  <fb:login-button onlogin="getProfile()">
    Get Profile
  </fb:login-button>

I get the expected response only if I am logged out of Facebook and subsequently log in through the dialog; if I click the button while I’m already logged in, I get this:

And if I push the response to the browser:

getProfile = function() {
  FB.api('/me', function(response) {
    console.log(response);
    var
      profile = document.getElementById('profile'),
      p = document.createElement('p');
    p.innerHTML = response.first_name;
    profile.appendChild(p);
  });
  return false;
};

Of course I get two paragraphs with my name in them.

Can anyone spot what I’m doing wrong? So far my Googling has me convinced that this is related to the way the SDK handles log in events (firing on every page load) but I can’t figure out how I’m supposed to account for that in the application code.

Answer 1

I believe the onlogin event fires when you load the page because you are logged into Facebook. Then, when your user clicks the button, it also triggers the event. If you’re not logged in in the first place, then the onlogin event doesn’t fire on load.

UPDATE: to avoid this, simply don’t hook the getProfile to the onlogin event except inside an if statement based on the FB.getLoginStatus method http://developers.facebook.com/docs/reference/javascript/FB.getLoginStatus/ Simply put, if you’re logged in, don’t attach an onlogin event, otherwise do an FB.Event.subscribe http://developers.facebook.com/docs/reference/javascript/FB.Event.subscribe/ on the onlogin event and your method will run whenever the user logs in through your XFBML-generated login button.

FB.getLoginStatus(function(response) {
if (response.status === 'connected') {
  //print the response data into the paragraph here
} else if (response.status === 'not_authorized') {
  // the user is logged in to Facebook, 
  // but has not authenticated your app
  FB.event.subscribe( 'auth.login', function(){
    getProfile();
  });
} else {
  // the user isn't logged in to Facebook.
}
});