PS. sorry for the split replies, but the form cut off the text in the middle of the code expample.

// Open and send the request for the file
this.XHRObject.open(’GET’,
File, // requested file
true); // asynchronous call

this.XHRObject.send(null);
};

// RequestAndRunScript()
// Requests a script file from the server and runs the script

CRequestObject.prototype.RequestAndRunScript = function (ScriptFile)
{
var _this = this;

// Define an onload function that will be called after loading the script
var onLoadFunction = function(XHRObject)
{
eval( XHRObject.responseText );
if (_this.onCompletion) {
_this.onCompletion();
}
};
// Load the script file and run it
this.RequestFile(ScriptFile, onLoadFunction);
};

// An example of an html-file’s onload function:

window.onload = function()
{
// Load and initialize the scripts
var RequestObject1 = new CRequestObject();
var RequestObject2 = new CRequestObject();
var RequestObject3 = new CRequestObject();
var RequestObject4 = new CRequestObject();
var RequestObject5 = new CRequestObject();
RequestObject1.onCompletion = function() { RequestObject2.RequestAndRunScript(’Script2.js’); };
RequestObject2.onCompletion = function() { RequestObject3.RequestAndRunScript(’Script3.js’); };
RequestObject3.onCompletion = function() { RequestObject4.RequestAndRunScript(’Script4.js’); };
RequestObject4.onCompletion = function() { RequestObject5.RequestAndRunScript(’Script5.js’); };
RequestObject5.onCompletion = function() { alert(’All scripts loaded’); };
RequestObject1.RequestAndRunScript(’Script1.js’);

// Initialize the application, do something useful…
var cp = new CCommandProcessor();

};

// Call the specified function
if (_this.XHRObject.status

I got your book this monday and I’m very pleased with it. I’ve been working with the Maps API for a while, but I still learn a lot from the book, in particular from the “Advanced” topics and from your hints on external sources for geocoding data.

For the loading dilemma, I use an approach that is in my opignion easier and more flexible:

1) put nothing but html in your html-file, don’t load any scripts by meta-tags except for the Google API.

2) show a “loading…” message in your html-file

3) in your onload() function, load your application’s scripts via XmlHttpRequest

4) when onreadystate == 4 for the first script loaded, eval() the script and then go on and load the next script etc., to make sure, the scripts get loaded and initialized in the correct order

5) load your data files the same way

6) Due to the way the browsers implement variable scopes, any global objects contained in the scripts must be defined implicit, i. e. without the ‘var’ keyword. E. g.:
Define: ‘myClass = function () {…}; ‘
Not: ‘var myClass = function…’ and not ‘function myClass()…’

An implementation of the above (error checking stripped off):

// The CRequestObject class implements the XHTML-Request-Object class

// Constructor
function CRequestObject ()
{
// Create an XMLHttpRequest-object (browser implementation dependend)
if (window.XMLHttpRequest) { // is Mozilla Firefox, Opera, Internet Explorer 7
this.XHRObject = new XMLHttpRequest();
}
else {
if (window.ActiveXObject) { // is Internet Explorer 6 or earlier
this.XHRObject = new ActiveXObject(”Microsoft.XMLHTTP”);
}
}
}

// RequestFile()
// Requests a file from the server and calls the specified function on completion

CRequestObject.prototype.RequestFile = function (File, onLoadFunction)
{
var _this = this; // a way to pass the this-pointer of the CRequestObject to the event handler (which overwrites the this pointer)

this.XHRObject.onreadystatechange = function ()
{
if(_this.XHRObject.readyState == 4) // complete
{
// Call the specified function
if (_this.XHRObject.status