Defer loading of Facebook Like Button Script

问题

Google pagespeed is complaining about my facebook like button script. How can I defer the script?

45KiB of JavaScript is parsed during initial page load. Defer parsing JavaScript to reduce blocking of page rendering. http://static.ak.facebook.com/.../xd_arbiter.php?... (21KiB of inline JavaScript) https://s-static.ak.facebook.com/.../xd_arbiter.php?... (21KiB of inline JavaScript) http://www.facebook.com/.../like.php?... (3KiB of inline JavaScript)

Here's the code I'm using and I'm loading it into a .js file in the footer of my page.

(function(d,s,id){
        var js,fjs = d.getElementsByTagName(s)[0];
        if(d.getElementById(id)){return;}
        js=d.createElement(s);
        js.id=id;
        js.async=true;
        js.defer=true;//THIS DOES NOT APPEAR TO SATISFY PAGESPEED
        js.src="//connect.facebook.net/en_US/all.js#xfbml=1";
        fjs.parentNode.insertBefore(js,fjs);
    }
    (document, "script", "facebook-jssdk")
);

Results in the following script tag (via Chrome's inspector):

    <script 
    id="facebook-jssdk" 
    async="" 
    defer="" 
    src="//connect.facebook.net/en_US/all.js#xfbml=1"></script>

回答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

回答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>

回答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")
);

来源：https://stackoverflow.com/questions/15349867/defer-loading-of-facebook-like-button-script

标签

jquery

facebook

deferred-loading