gistfile1.js

  /**
   *  Element#clone(@element, deep) -> Element
   *  
   *  Returns a duplicate of an element. 
   *  A wrapper around DOM Level 2 Node::cloneNode, 
   *  which takes care of clone's expando properties defined by Prototype
   *  
   *  `deep` argument is passed along to a an underlying `cloneNode` 
   *  and affects cloning correspondingly - i.e. skipping child nodes if `false`
  **/
  clone: function(element, deep) {
    if (!(element = $(element))) return;
    var clone = element.cloneNode(deep);
    clone._prototypeUID = void 0;
    if (deep) {
      var descendants = Element.select(clone, '*'),
          i = descendants.length;
      while (i--) {
        descendants[i]._prototypeUID = void 0;
      }
    }
    return clone;
  }

...

testElementClone: function() {
  var element = new Element('div', {
    className: 'foo',
    title: 'bar'
  });
  
  // add child
  element.update('<span id="child">child node</span>');
  
  // add observer
  element.observe('click', Prototype.emptyFunction);
  
  // add observer on a child
  element.down('span').observe('dblclick', Prototype.emptyFunction);
  
  var shallowClone = element.clone();
  var deepClone = element.clone(true);
  
  var assertCloneTraits = (function(clone) {
    this.assert(clone); // exists
    this.assert(clone.show); // is extended
    this.assertEqual('DIV', clone.nodeName.toUpperCase()); // proper nodeName
    this.assertEqual('foo', clone.className); // proper attributes
    this.assertEqual('bar', clone.title);
    this.assert(!clone._prototypeUID); // _prototypeUID does not exist
  }).bind(this);
  
  // test generic traits of both deep and shallow clones first
  assertCloneTraits(shallowClone);
  assertCloneTraits(deepClone);
  
  // test deep clone traits
  this.assert(deepClone.firstChild);
  this.assertEqual('SPAN', deepClone.firstChild.nodeName.toUpperCase());
  this.assert(!deepClone.down('span')._prototypeUID);
}