Query XPath

xpath.js

function queryXPath(expr, ctx, type){
    ctx = ctx || document;
    type = type || XPathResult.ANY_TYPE;
    var doc = ctx.nodeType === Node.DOCUMENT_NODE ? ctx : ctx.ownerDocument;
    var nsResolver = doc.createNSResolver(doc.documentElement);
    var arr = [], i = null;
    try {
        expr = ("" + expr).replace(/\bhasClass\(["'](\w+)["']\)/, function(expr, className){
            return "contains(concat(' ', normalize-space(@class), ' '), ' " + className + " ')";
        });
        var res = doc.evaluate(expr, ctx, nsResolver, type, null);
        type = res.resultType;
        if(type === XPathResult.NUMBER_TYPE) {
            return res.numberValue;
        } else if (type === XPathResult.STRING_TYPE) {
            return res.stringValue;
        } else if (type === XPathResult.BOOLEAN_TYPE) {
            return res.booleanValue;
        } else if (type === XPathResult.UNORDERED_NODE_ITERATOR_TYPE || type === XPathResult.ORDERED_NODE_ITERATOR_TYPE) {
            while((i = res.iterateNext()) !== null) {
                arr.push(i);
            }
            return arr;
        } else if (type === XPathResult.UNORDERED_NODE_SNAPSHOT_TYPE || type === XPathResult.ORDERED_NODE_SNAPSHOT_TYPE) {
            for (i = 0; i < res.snapshotLength; i++ ) {
                arr.push(res.snapshotItem(i));
            }
            return arr;
        } else if (type === XPathResult.ANY_UNORDERED_NODE_TYPE || type === XPathResult.FIRST_ORDERED_NODE_TYPE) {
            return res.singleNodeValue;
        } else {
            throw new Error('Unknown result type ' + type);
        }
    } catch(e) {
        console.log(e);
        return null;
    }
}