FB init

fb_init.html

<div id="fb-root"></div>
<script>
  var fbAppId = '< APP ID >';
  
  (function(){

    var fbInitFuncs = [];
    var fbInitialized = false;

    window.fbAsyncInit = function() {
      fbInitialized = true;
      FB.init({
        appId  : '< APP ID >',
        status : true,
        cookie : true,
        xfbml  : true
      });
      for(var i=0; i < fbInitFuncs.length; i++){
        fbInitFuncs[i]();
      }
    };

    window.onFbInit = function(func){
      if(fbInitialized){
        func();
      }
      else{
        fbInitFuncs.push(func);
      }
    }
  })();

  (function() {
    var e = document.createElement('script');
    e.src = document.location.protocol + '//connect.facebook.net/en_US/all.js';
    e.async = true;
    document.getElementById('fb-root').appendChild(e);
  }());
</script>