<div>
    <h2>You know, I am a Heading!</h2>
    <ul>
        <li>I am the first li</li>
        <li>I am the second li</li>
        <li>I am the third li</li>
    </ul>
</div>

<button onclick="go()" style="width:100px">Go!</button>

<script>
function go() {
  var childNodes = document.body.childNodes;
  for(var i=0; i<childNodes.length; i++) {
    var domElement = childNodes[i];
            doSomethingWithTheReturnedTag();
  }
}
</script>

<script>
    function go() {
    var items = startElem.getElementsByTagName("*");
    for (var i = items.length; i--;) {
       //perform operation on elment
    }
    }
 </script>