js实现xpath解析

function parse(STR_XPATH) { 
    var xresult = document.evaluate(STR_XPATH, document, null, XPathResult.ANY_TYPE, null);
    var xnodes = []; 
    var xres; 
    while (xres = xresult.iterateNext()) {
        xnodes.push(xres);
    }
    return xnodes;
};
var title = parse('//title/text()');
console,log(title)