Better Marketo / Salesforce munchkin.js loading that won't fire initMunchkin twice in IE.

gistfile1.js

<script type="text/javascript">
  (function() {
    function initMunchkin() {
      Munchkin.init('YOUR-ID');
      
      // custom handling after marketo is ready
      if (typeof marketo_ready != 'undefined') marketo_ready();
      
    }
    var s = document.createElement('script');
    s.type = 'text/javascript';
    s.async = true;
    s.src = document.location.protocol + '//munchkin.marketo.net/munchkin.js';
          
    if (s.readyState) { // IE, incl. IE9
      s.onreadystatechange = function() {
        if (s.readyState == "loaded" || s.readyState == "complete") {
          s.onreadystatechange = null;
          initMunchkin();
        }
      };
    } else { // Other browsers
      s.onload = initMunchkin;
    }
    ( document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0] ).appendChild( s );
  })();
</script>