function rawurlencode(str) {
  try {
    return encodeURIComponent(str)
          .replace(/!/g,  "%21")
          .replace(/'/g,  "%27")
          .replace(/\(/g, "%28")
          .replace(/\)/g, "%29")
          .replace(/\*/g, "%2A")
          .replace(/~/g,  "%7E");
  } catch(e) {
    return escape(str)
          .replace(/\+/g, "%2B")
          .replace(/\//g, "%2F")
          .replace(/@/g,  "%40");
  }
}

document.getElementById("ajaxtree").onclick = function(event) {
  var baseUrl = "html/ajaxtree/";

  var event   = event || window.event;
  var element = event.target || event.srcElement;

  if (element.nodeName == "LI") {
    var li = element;
    var ul = li.getElementsByTagName("ul")[0];

    if (li.className == "expanded") {
      li.className = "collapsed";
      ul.style.display = "none";
    } else if (li.className == "collapsed") {
      if (ul) {
        li.className = "expanded";
        ul.style.display = "block";
      } else {
        var req = window.ActiveXObject ? new ActiveXObject("Microsoft.XMLHTTP") : new XMLHttpRequest();
        if (req) {
          var a    = li.getElementsByTagName("a")[0];
          var name = rawurlencode(a.title).replace(/%/g, "%25");
          var url  = baseUrl + name + ".html";

          req.onreadystatechange = function() {
            if (req.readyState == 4 && req.status == 200) {
              li.className = "expanded";
              li.innerHTML += req.responseText;
            }
          }
          req.open("GET", url, true);
          req.setRequestHeader("If-Modified-Since", "Thu, 01 Jan 1970 00:00:00 GMT");
          req.send("");
        }
      }
    }
  }
}