This is a Javascript class that I wrote to make all that
whacky AJAX stuff a bit easier to deal with. It accounts
for browser differences, and seems to be quite robust.
This form is a very simple example of the ajax class in operation. You
can download the Javascript, XHTML and PHP source yourself here (Connects
to an aggregate SourceForge Project).
It consists of three source files: A Javascript
file, containing
the class itself, an XHTML file that contains a simplified
version of this page, and a very simple PHP file to provide
a server response.
Here's Why You Might Want to Use This Class
This class does not provide an "AJAX in a box" functionality.
It is a low-level driver. Think of it as the Transport
Layer in the OSI
model. Nevertheless, what it gives you is rock-solid, predictable
AJAX that works on all of the following browsers:
IE 5.0 (Windows 98SE) and all subsequent Windows versions of IE, Safari
1.2 and up, Netscape 7 and up, all versions of Mozilla and
Firefox, iCab 2.9 and up, and Opera 8 and above. All other
modern browsers against which I've tested work with this.
It does not work on Netscape 6 or earlier, or on Opera 7 or earlier.
It will not work on any Mac version of IE or on Safari 1.0.
It is SOLID. It won't start a new request until the
first one has completed. If you bang around on the icons
below, you will see each and every one complete (eventually).
If you use the form to submit POST and GET while the icons
are spinning, it will wait until the icons have stopped
before submitting the form, and vice-versa. It may seem
like threading is preferable, but, in most cases, it is
not. This is basic usability. Don't have too much stuff
going on. This is NOT the same as a host application, in
which threads are being resolved and managed locally.
That being said, there are some applications where threading can be
useful. In these cases, I have a threading driver, and you
should couple it with "tricks" to try to increase the number
of concurrent HTTPRequests supported by the browser. Otherwise,
as you will see in the threading demo, you won't actually
get any advantage.
These files demonstrate the basic use of AJAX in both GET and POST methods,
as well as a bit of basic DHTML.
The form below allows you to enter some text into a box, send it to
the server in either a GET or a POST transaction, then have
the page updated by the callback.
The nice thing about this class is that you don't have to worry about
POST transactions. You simply specify a URI as if it were
a GET, and the class strips out the parameters for separate
submission.
One item of particular interest in this class is that it allows you
to send a separate parameter to the callback, which can
be used to establish a context (callbacks are usually pretty
context-free, and AJAX doesn't have much support for reestablishing
the context).
NOTE: The Thread Driver (as of Version 1.4.19) will
probably be my implementation choice henceforth. It is lighter
and more robust than the queue.
NOTE: Thanks to Jeremy
Lucier, who gave me a new object
instatiation method that covers variants of Microsoft XMLHTTP
class. I have implemented the new method in 1.4.17.
NOTE: Thanks
to Diane Benroth for alerting me to an issue with IE (Surprise,
surprise, surprise) that I was able to track down and fix toot sweet in
Version 1.4.3.
UPDATE: You might like my AJAX Threading
Driver.
UPDATE: In 1.4.10, I added a "SimpleAJAXCall()" function
that makes this class the very simplest AJAX implementation
I've ever seen. Read the comments in the JavaScript
File.
If you want to see SimpleAJAXCall() in action, check
out this file.
Do a "View Source" to see how truly, obnoxiously simple
it is.
UPDATE: It turns out that I'm mistaken about my belief
that you only get one timeout (Thanks for setting me straight, FotiMan).
I'd let someone's bad implementation of it convince me wrong,
and I should have done more research. In any case, this
is good news, as it means I can implement some timeout handlers.
I'll do that in an upcoming version.
