I'm getting the exception below from Firefox, IE works fine. The code is very similar to your sample:

function init() {
  var oReq = zXmlHttp.createRequest();
  oReq.onreadystatechange = function () {
    if (oReq.readyState == 4) {
      // only if "OK"
      if (oReq.status == 200) {
        alert(oReq.responseText);
      }
    }
  };
oReq.open("GET", "http://localhost:8989/mpc10/LocLoader.jsp", true);
oReq.send();
}

The function above is contained in MpcAjaxLocationLoader.htm and gets called onload.

Error: uncaught exception: [Exception... "Not enough arguments [nsIXMLHttpRequest.send]" nsresult: "0x80570001 (NS_ERROR_XPC_NOT_ENOUGH_ARGS)" location: "JS frame :: http://localhost:8989/AjaxTest/MpcAj...tionLoader.htm :: init :: line 23" data: no]

This isn't a zXML error. You must pass a value to send() in Firefox, even if the value is null. So you should be doing:

Nicholas C. Zakas
Author, Professional JavaScript for Web Developers (ISBN 0764579088)
http://www.nczonline.net/

In your chapter 4 code, you use:

oReq.send();

instead of what you just suggested:

oReq.send(null);

Even after making that change, the cross browser code does not work in IE or Firefox.

I'll dig deeper to see if I can find the error.

If you let me know what error you're getting, I can try to help figure out the problem.

Nicholas C. Zakas
Author, Professional JavaScript for Web Developers (ISBN 0764579088)
http://www.nczonline.net/

I had this problem in chapter 2/page 37 and found that if the info.txt doesn't exist the status check just gives a generic undefined message never reaching the "else" alert

Actually I found the problem was in checking for the status when onreadystate was not 4(complete)

I found this when trying to run the site from VS.NET and it kept crashing with an msxml3.dll error

What was the solution?