addLinks() - find URLs in a piece of text

This snippet take a block of text and an element name and returns an element of that type with the text in it and all URLs turned into a-hrefs:

function addLinks(text, tagName){
	var urlRE = /(http:[\;\/\?\\@\&\=\+\$\,\[\]A-Za-z0-9\-_\.\!\~\*\'\(\)%][\;\/\?\:\@\&\=\+\$\,\[\]A-Za-z0-9\-_\.\!\~\*\'\(\)%#]*)/g;
	var cruft = /([\]\)\,\.\'\"\;]+)$/;
	var span = document.createElement(tagName);
	var c = 0;
	text.replace(urlRE, function(m,a1,p){
		// Add the text that occurred between our last result and this one as plain text
		span.appendChild(document.createTextNode(text.substring(c,p)));
		a1 = a1.replace(cruft,'');
		c=p+a1.length;

		// Add the URL as an a-href
		var a = document.createElement('a');
		a.href = a1;
		a.appendChild(document.createTextNode(a1));
		span.appendChild(a);
	});
	if(text.substr(c))
		span.appendChild(document.createTextNode(text.substr(c)));
	return span;
}