javascript pass element from one function to another

this is a partial code:

function readXmlUsingXPath(i,guid, xpath) {
    var xmlDoc = loadXML("gameFeed.aspx?guid=" + guid);
    if (xmlDoc == null) { document.getElementById(guid).innerHTML = "UPDATING"; return }
    else { };
    i.innerHTML = xmlDoc.selectNodes(xpath)[0].text;
}

window.onload = function () {
    for (var i = 0; i < document.getElementsByTagName('jackpot').length; i++) {
        var guid = document.getElementsByTagName('jackpot')[i].getAttribute('data-g').split('|')[0];
        var xpath = document.getElementsByTagName('jackpot')[i].getAttribute('data-开发者_开发百科g').split('|')[1];
        readXmlUsingXPath(document.getElementsByTagName('jackpot')[i],guid, xpath);
    }
}

basicly, what i want to do is pass the element from the onload function, to the readXmlUsingXpath function, so i could change it. but i get an unknown runtime error...

as asked, some sample html:

<li>
<a href="/gamepath/"><span>gameTitle</span>
<span><jackpot data-g="<%=game.Guid %>|<%=game.GamingProperties.JackpotFeedXpath %>">UPDATING . . .</jackpot></span>
</a>
</li>

Well, first of all, yes - cache the results of getElementsByTagName() and .getAttribute('data-g').split('|') into a variable:

var myDataG = MyJackpotElement.getAttribute('data-g').split('|');

Then instead of processing XPath that comes from your HTML source code, since you pass the guid to a server side script anyway, make the server script process the item (with XPath) on the server side - so it would get the xpath expression from the item you're loading by Guid :)

Make the server side script return you the value you're looking for (gameFeed.aspx?guid=), not the XML that you will further process on the client side to find the value.

Does the code work after refactoring it as per Denis’s suggestions?

One big problem with the way you kept performing a getElementsByTagName, even aside from the huge performance hit, is that if the collection changes for any reason, the length might not be correct anymore, and you could be requesting element 9 where only 8 exist.

Also, it’s possible that changing the innerHTML of an element will throw the browser off.

Side nit: I’ve renamed the i parameter of the readXmlUsingXPath function to jackpot, which seems a little more appropriate than just i.

function readXmlUsingXPath(jackpot, guid, xpath) {
    var xmlDoc = loadXML("gameFeed.aspx?guid=" + guid);
    if (xmlDoc == null) {
        document.getElementById(guid).innerHTML = "UPDATING"; 
        return;
    }
    var firstNode = xmlDoc.selectNodes(xpath).item(0);
    jackpot.innerHTML = firstNode.text;
}

window.onload = function () {
    var jackpots = document.getElementsByTagName('jackpot');
    for (var i = 0; i < jackpots.length; i++) {
        var data = jackpots[i].getAttribute('data-g').split('|'),
        guid = data[0],
        xpath = data[1];
        readXmlUsingXPath(jackpots[i], guid, xpath);
    }
}

ok, so i modified the code a bit, and made it simpler.

now it works as its supposed to.

function loadXMLDoc(guid,xpath,i) {

    var xmlhttp;
    if (window.XMLHttpRequest) {xmlhttp = new XMLHttpRequest();}
    else {xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");}
    xmlhttp.async = true;
    xmlhttp.onreadystatechange = function () {
        if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
            i.innerHTML = xmlhttp.responseXML.selectNodes(xpath)[0].text;
        }
    }
    xmlhttp.open("GET", "gameFeed.aspx?guid=" + guid, true);
    xmlhttp.send();
}

var tags = document.getElementsByTagName("pre");
for (var i = 0; i < tags.length; i++) {
    var data = tags[i].getAttribute('data-g').split('|'), guid = data[0], xpath = data[1];
    loadXMLDoc(guid,xpath,tags[i]);
}