gistfile1.js

function wrapSpan(node, index) {
 	if(node.nodeName === '#text') {
 		var text = node.textContent;
 		var s = document.createElement('span');

 		s.textContent = text;
 		node.parentElement.insertBefore(s, node.parentElement.childNodes[index]);
 		node.remove();
 		
 	} else {
 		var length = node.childNodes.length;
 		// childNodes is a collection, not an array. :-/
 		for(var i = 0; i < length; i++)
 			wrapSpan(node.childNodes[i], i);
 	}
 }