Browser-independent XPath with Javascript

Now that you’re able to load XML and transform it using an XSL stylesheet, wouldn’t it be handy to also be able to perform XPath selects/functions on that XML outside of the stylesheet’s formatting? Why, yes. Yes, it would:

Javascript code:

function xpSelect(xmlDoc, xpathStr)
{
    try {
        if(xmlDoc.evaluate) {
            // WebKit (Safari, Chrome), Mozilla/Firefox, Opera, etc.
            var xpr = xmlDoc.evaluate(xpathStr, xmlDoc, null, XPathResult.
                UNORDERED_NODE_ITERATOR_TYPE, null);
            var cur = xpr.iterateNext();
            var a = 0;
            var retarr = [];

            // build array from returned nodes
            while(cur) {
                retarr[a++] = cur;
                cur = xpr.iterateNext();
            }

            return(retarr);
        } else {
            // Internet Explorer
            return(xmlDoc.selectNodes(xpathStr));
        }
    } catch(e) {
        alert("Error:\n" + e.message);
        return false;
    }
}

It’s worth noting that IE’s selectNodes() method is drastically slower than the standard evaluate() method, but this function’s results will be the same: an array of element objects. The function is rather base in its implementation, but could be modified to return custom data sets (or a DOM tree/node) instead of an array. Either way, //state[@name=’Alabama’]/areacode is just a function call away!