jQuery Bookmarklet

+jQuery.js

(function() {
  var otherLib = (typeof($) == 'function');

  if (typeof(jQuery) != 'undefined') {
    alert('jQuery already defined');
    return;
  }

  function getScript(url, callback) {
    var script = document.createElement('script');
    script.src = url;

    var head = document.getElementsByTagName('head')[0],
        done = false;

    script.onload = script.onreadystatechange = function() {
      if ( !done && (!this.readyState
        || this.readyState == 'loaded'
        || this.readyState == 'complete') ) {
        done = true;
        callback();
        script.onload = script.onreadystatechange = null;
        head.removeChild(script);
      }
    };
    head.appendChild(script);
  }

  getScript('http://code.jquery.com/jquery-latest.min.js', function() {
    if (typeof jQuery == 'undefined')
      alert('Unable to load jQuery');
    else if (otherLib)
      alert('No conflict mode, use $jq()');
    else
      alert('jQuery is loaded');
  });
})();