Ext JS is a JavaScript Library/Framework which works in conjunction with Prototype, YahooUI and jQuery. It’s probably the most exciting toolkit available for building web 2.0 websites right now. It’s jam packed with features, and is designed to make life much easier for building great UI in JavaScript.

I’ll not dig to deep right now, I suggest you check out the example and demos first to see what you think.

Below is a the script used to grab XML data via Ajax and populate a grid (sortable table like object):

To understand how AJAX works, we will create a small AJAX application.

First, we are going to create a standard HTML form with two text fields: username and time. The username field will be filled in by the user and the time field will be filled in using AJAX.

The HTML file will be named "testAjax.html", and it looks like this (notice that the HTML form below has no submit button!):

Here is a simple, quick way to validate required form fields using AJAX, PHP and MySQL. What we’re going to do is display an error message to the right of the required field, and if there are errors, restrict the submit button. And if a user were to skip a required field, or leave it blank, we’ll highlight it along with removing the submit button.

I feel this is useful because it validates on the fly using PHP methods that we may already have in place – there is no need to learn the “Javascript way” to do something that you’ve been doing for a while. I make a few assumptions in this tutorial. The first is that you have a basic understanding of PHP and how to connect to a MySQL database and retrieve records. Along with that, for this tutorial, you’ll need a table setup with usernames and email addresses stored in it; my table will be called “users.” The second is that you have some understanding of how AJAX works. Third is that you have an understanding of CSS and how to define classes and id’s. You could figure these things about by going through this tutorial, but it would be a lot easier on you if you do understand what I laid out.

This example is probably the simplest example you will ever find.
We are going to use the prototype feature ‘ajax.Updater’ (see part one for more details on prototype).

ajax.Updater allows you to specify an element ID and script URL - and whatever the script URL prints will appear in your element ID. Simple as that.

The example below simply returns the Server time each time the button is clicked.

I’m not going to explain this bit by bit as it is just so easy to grasp.

Remember, you will need the prototype library in order to use this!

Fjax is an open, lightweight, cross-browser methodology for Ajax-style web 2.0 development
Fjax is a technique focused on drastically streamlining the XML handling layer of web 2.0 applications. Picture Ajax's XML parsing and handling with less than 65 lines of code! It's not a replacement for toolsets that provide presentation-layer visual gizmos. Think of it as a new engine to put under the hood of all the great widgets that are already out there.