Add a "getXPath" method to the prototype for HTML element nodes

getXPath.js

window.HTMLElement.prototype.getXPath = function() {
	// special cases
	if (this.id) return '//*[@id="' + this.id + '"]';
	if (this.tagName.toLowerCase() === 'html') return '/html';

	var count = 0, index, nodes = this.parentNode.childNodes;

	for (var i = 0; i < nodes.length; i++) {
		if (nodes[i].nodeType !== 1 || nodes[i].tagName !== this.tagName) continue;
		count++;
		if (nodes[i] === this) index = count;
	}

	return this.parentNode.getXPath() + '/' + this.tagName.toLowerCase() + (count > 1 ? '[' + index + ']' : '');
}