Traverse DOM elements recursively.

walk-dom-with-callback.js

var walkDom=function(html_elem, func)
{
	if(typeof func!='function') return;
	var loop=function(html_elem)
	{
		do
		{
			func(html_elem); // call callback for every element
			if(html_elem.hasChildNodes())
				loop(html_elem.firstChild);
		}while(html_elem=html_elem.nextSibling);
	};
	loop(html_elem);
	//loop(html_elem.firstChild); // do not include siblings of start element
}

var fn=function(html_elem)
{
	console.log('Elem:', html_elem);
}

walkDom(document.body, fn);

walk-dom.js

function walkDom(start_element)
{
	var arr=[]; // we can gather elements here
	var loop=function(element)
	{
		do{
			// we can do something with element
			if(element.nodeType==1) // do not include text nodes
				arr.push(element);
			if(element.hasChildNodes())
				loop(element.firstChild);
		}
		while(element=element.nextSibling);
	}
	loop(start_element);
	//loop(start_elem.firstChild); // do not include siblings of start element
	return arr;
}

walkDom(document.body);