Facebook OAuth2 client side.

facebook.js

var Facebook = {

  init: function(){
    if(!GLOBAL_SETTINGS.FBappId){ return; }
    if(GLOBAL_SETTINGS.application_name){
      Facebook.authorize_message = "Authorize your Facebook account for " + GLOBAL_SETTINGS.application_name;
    }
    Facebook.load_fb();
    $('#facebook_connect').on('click', function(e){
      e.preventDefault();
      Facebook.login();
    });
  },

  login: function(){
    FB.login(function(response){}, { scope: 'publish_stream,email' });
  },

  finish: function(response){
    window.location.href = '/users/auth/facebook/callback?state='+ GLOBAL_SETTINGS.state;
  },

  message: function(msg){
    $('#fb_connect_message').text(msg);
    $('#fb_connect_message').show();
  },

  load_fb: function(){
    window.fbAsyncInit = function() {
      FB.init({
        appId      : GLOBAL_SETTINGS.FBappId,
        status     : false, // don't check login status
        cookie     : true, // enable cookies to allow the server to access the session
        xfbml      : true  // parse XFBML
      });

      FB.Event.subscribe('auth.authResponseChange', function(response) {
        if(response.status === 'connected'){
          if(response.authResponse){
            Facebook.finish(response);
          }
        } else if (response.status === 'not_authorized'){
          Facebook.message(Facebook.authorize_message);
        } else {
          FB.login();
        }
      });
    };

    // Load the FB SDK asynchronously
    (function(d){
     var js, id = 'facebook-jssdk', ref = d.getElementsByTagName('script')[0];
     if (d.getElementById(id)) {return;}
     js = d.createElement('script'); js.id = id; js.async = true;
     js.src = "//connect.facebook.net/en_US/all.js";
     ref.parentNode.insertBefore(js, ref);
    }(document));

  }

};