DocType extraction snippet

doctype.js

function getDocType(document) {
	var node = document.firstChild;
	while (node) {
		var nodeType = node.nodeType;
		if (nodeType === 10) {
			// doctype
			var doctype = '<!DOCTYPE '+(document.documentElement.tagName || 'html').toLowerCase();
			if (node.publicId) {
				doctype += ' PUBLIC "' + node.publicId + '"';
			}
			if (node.systemId) {
				doctype += ' "' + node.systemId + '"';
			}
			return doctype+'>';
		}
		if (nodeType === 8 && (""+node.nodeValue).toLowerCase().indexOf("doctype") === 0) {
			// IE represents DocType as comment
			return '<!' + node.nodeValue + '>';
		}

		node = node.nextSibling;
	}

	return "";
}