Defer loading of Facebook Like Button Script

Question 1

Use the setTimeout luke!

setTimeout( function () {
   (function(d,s,id){
         // load js
         ...
      }
      (document, "script", "facebook-jssdk")
   );
}, 3000);

You can throw the load in another 'thread' to async or Defer it

Question 2

setTimeout works but it's not real defer, since if the page finished loading after the time set (in this case 3 seconds) the like button will be loaded before the page finished loading.

I put the like button's javscript code inside my own function and nested it inside the

<script>
    function FbButtonLoad(){
      (function(d,s,id){
         // load js
         ...
      }
      (document, "script", "facebook-jssdk")
   );
}
</script>

then I set it in the body tag to run on page load:

<body onload="FbButtonLoad();">

The button appears on the page where I left it's containers:

<div id="fb-root"></div>
<div class="fb-like" data-send="true" data-width="350" data-show-faces="true"></div>

Question 3

Another slightly less than perfect solution (HTML5 only) would be to load the library on DOMContentLoaded.

document.addEventListener('DOMContentLoaded', function() {
    (function(d,s,id){
        var js,fjs = d.getElementsByTagName(s)[0];
        if(d.getElementById(id)){return;}
        js=d.createElement(s);
        js.id=id;
        js.src="//connect.facebook.net/en_US/all.js#xfbml=1";
        fjs.parentNode.insertBefore(js,fjs);
    }
    (document, "script", "facebook-jssdk")
);