// Adapted from: http://www.anyexample.com/webdev/javascript/javascript_getelementsbyclass_function.xml

function getElementsByClass(searchClass, domNode, tagName) {
    if (domNode == null)
        domNode = document;
    if (tagName == null)
        tagName = "*";
    var els = new Array();
    var tags = domNode.getElementsByTagName(tagName);
    var tcl = " " + searchClass + " ";
    for (var i = 0, j = 0; i < tags.length; i++) {
        var test = " " + tags[i].className + " ";
        if (test.indexOf(tcl) != -1)
            els[j++] = tags[i];
    }
    return els;
}

function show(cl) {
    var els = getElementsByClass(cl, null, "div");

    for (var i = 0; i < els.length; i++) {
        // hide every element with els[i]'s first class
        var classes = els[i].className;
        var firstClassIdx = classes.indexOf(" ");
        if (firstClassIdx != -1) {
            var altClass = classes.substring(0, firstClassIdx);
            var alts = getElementsByClass(altClass, null, "div");
            for (var j = 0; j < alts.length; j++)
                alts[j].style.display = "none";

            // show element with given class
            els[i].style.display = "";
        }
    }
}