common Xpath solution across browser

//select single node

function selectsingleNode(context, expression, namespaces) {
        var doc = (context.nodeType != 9 ? context.ownerDocument : context);

        if (typeof doc.evaluate != "undefined") {
            var nsresolver = null;
            if (namespaces instanceof Object) {
                nsresolver = function (prefix) {
                    return namespaces[prefix];
                };
            }

            var result = doc.evaluate(expression, context, nsresolver, XPathResult.FIRST_ORDERED_NODE_TYPE, null);
            return (result !== null ? result.singleNodeValue : null);
        } else if (typeof context.selectSingleNode != "undefined") {

            //create namespace string
            if (namespaces instanceof Object) {
                var ns = "";
                for (var prefix in namespaces) {
                    if (namespaces.hasOwnProperty(prefix)) {
                        ns += 'xmlns:' + prefix + "='" + namespaces[prefix] + "'";
                    }
                }
                doc.setProperty("SelectionNamespaces", ns);
            }
            return context.selectSingleNode(expression);
        } else {
        throw new Error("no xpath engine found");
        }
    }

//select nodes

function selectNodes(context, expression, namespaces) {
        var doc = (context.nodeType != 9 ? context.ownerDocument : context);

        if (typeof doc.evaluate != "undefined") {
            var nsresolver = null;
            if (namespaces instanceof Object) {
                nsresolver = function (prefix) {
                    return namespaces[prefix];
                };
            }

            var result = doc.evaluate(expression, context, nsresolver, XPathResult.ORDERED_NODE_SNAPSHOT_TYPE, null);
            var nodes = new Array();

            if (result != null) {
                for (var i = 0, len = result.snapshotLength; i < len; i++) {
                    nodes.push(result.snapshotItem(i));
                }
            }

            return nodes;
        } else if (typeof context.selectNodes != "undefined") {

            //create namespace string
            if (namespaces instanceof Object) {
                var ns = "";
                for (var prefix in namespaces) {
                    if (namespaces.hasOwnProperty(prefix)) {
                        ns += "xmlns:" + prefix + "='" + namespaces[prefix] + "'";
                    }
                }
                doc.setProperty("SelectionNamespaces", ns);
            }
            var result = context.selectNodes(expression);
            var nodes = new Array();

            for (var i = 0, len = result.length; i < len; i++) {
                nodes.push(result[i]);
            }

            return nodes;
        } else {
        throw new Error("no xpath engine found");
        }
    }