title: asynchronous javascript loading/executing
body: <p>In this post, <a href="https://stackoverflow.com/questions/2774373/asynchronous-js-file-loading-syntax">asynchronous .js file loading syntax</a>, someone said, "If the async attribute is present, then the script will be executed asynchronously, as soon as it is available." </p>
  
  <pre><code>(function() {
    var d=document,
    h=d.getElementsByTagName('head')[0],
    s=d.createElement('script');
    s.type='text/javascript';
    s.async=true;
    s.src='/js/myfile.js';
    h.appendChild(s);
  }()); /* note ending parenthesis and curly brace */
  </code></pre>
  
  <p>My question is, what does "the script will be executed asynchronously" mean? Will this script be executed in a different thread from other javascripts in the page? If yes, should we worry about synchronization issue in the two threads?</p>
  
  <p>Thanks.</p>