Facebook Init detector!

FB.init.detector.js

// Sample of usage
$(document).bind('FB.ready',function(){
  console.log('FB is ready');
  FB.api('/me',function(response){
    console.log(response);
  });
});

// Init Detector
var _FB = {
   count: 0
  ,interval : setInterval(function(){
      try{
        if(FB._session && (typeof FB._session !== 'undefined')){
          clearInterval(_FB.interval);
          $(document).trigger('FB.ready');
        }
      } catch(e){
        if(_FB.count++ > 100) {
          clearInterval(_FB.interval);
          throw new Error('`FB` hasn\'t become available.');
        }
      }
    },15)
};