simple_load.js

var loadScript = (function(global) {

  return function(url) {

    var script,

    // document reference
    doc = global.document,

    // root element reference
    root = doc.documentElement,

    // head element reference to add scripts
    head = doc.getElementsByTagName('head')[0] || root;

    // inject a script as first element in the head section
    script = head.insertBefore(doc.createElement('script'), head.firstChild);
    script.type = 'text/javascript';
    script.src = url;

    // need a small IE inference :(
    // to avoid problems with Opera
    // doesn't this make sense :?)
    if (doc.createEventObject) {
      // setup script 'readystatechange' handler
      script.onreadystatechange =
        function() {
          if (/loaded/.test(script.readyState)) {
            init();
          }
        };
    } else {
      // setup script 'load' handler
      script.onload = init;
    }

  };

})(this);

function init() {
  // do stuff here after script has loaded
}