outerHTML

outerHTML.htm

<script>
HTMLElement.prototype.__defineGetter__('outerHTML', function(){
  var _ = this.ownerDocument.createElement('_');
  _.appendChild(this.cloneNode(true));
  return _.innerHTML;
});
HTMLElement.prototype.__defineSetter__('outerHTML', function(h){
  var r = this.ownerDocument.createRange();
  r.selectNode(this);
  this.parentNode.replaceChild(r.createContextualFragment(h), this);
});

function onload(){
  document.body.outerHTML =
    '<xmp>' + document.querySelector('script').outerHTML;
}
</script>