title: Identify elements of function javascript
body: <p>I got the function automatically generated by facebook for a like button plugin code. However, I'm not quite sure about the variables in the function, and I would be really grateful if anyone helps me find out what does each mean.</p>
  
  <p>The <code>html</code> the function gathers data from:</p>
  
  <pre><code>    &lt;div class="fb-like" data-href="https://www.facebook.com/yanntiersen.official"   
  data-send="true" data-width="450" data-show-faces="true" data-font="arial"&gt;&lt;/div&gt;
  </code></pre>
  
  <p>The actual javascript function:</p>
  
  <pre><code>&lt;script&gt;(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_GB/all.js#xfbml=1&amp;appId=123456789";
    fjs.parentNode.insertBefore(js, fjs);
  }(document, 'script', 'facebook-jssdk'));&lt;/script&gt;
  </code></pre>
  
  <p>I see that the function is called for <code>(document, 'script', 'facebook-jssdk')</code>, but I don't really understand how things work.
  Can anyone explain me this, please?</p>