var parent = document.getElementById('parent'),

    child = document.getElementById('child'),

    grandChild = document.getElementById('grandChild');

​

console.log(child.outerHTML);

​

/* logs:

<div id="child">

​

  <div id="grandChild">

    <p>Some text for grandchild.</p>

  </div>

​

  <p>Some text for child.</p>

</div>

*/

​

grandChild.outerHTML = '<p>New paragraph</p>';

console.log(document.getElementById('grandChild')); // null