Please, someone tell me there is a built in way to do this. But in the interim, since I don’t know of another way, if you’re looking for a child of a given node (by name), you can do it something like this.

    // Used to store the matched node, if found.
    var _jsMatchedNode;
 
    function jsFindChildByName(pvNodeName, pvParent)
    {
        if (pvParent.nodeName.toLowerCase() == pvNodeName.toLowerCase())
        {
            _jsMatchedNode = pvParent;
            return;
        }
 
        if (!pvParent.childNodes) return;
 
        if (pvParent.childNodes.length == 0) return;
        var nodeList = pvParent.childNodes;
        for(var x=0;x<nodeList.length;x++)
        {
               jsFindChildByName(pvNodeName, nodeList[x]);
        }
    }

Of course if you use this repeatedly it would behoove you to reset the _jsMatchedNode variable before each use.