Tricklin

As I mentioned in my previous post, I planned on creating a "tutorial that will walk you through a real world working example of AJAX using ColdFusion and a simple MS Access Database." Well, here it is:

In order to represent a working example of AJAX, there are a few things we're going to need.

• database
• HTML file
• JavaScript (located within the HTML file in this example)
• ColdFusion file (note: any programming language can be used)
• prototype JavaScript library

The Database

The database used in this example is an extremely basic MS Access database consisting of one table that contains 6 fields:

Now that we know what we are going to be storing, let's take a look at the ".html" file.

HTML File

This file will consist of the form fields needed to populate the database, along with the placeholder we will use to show the information being stored:

<form name="addEmployee">
First Name:<input type="text" name="FirstName" id="FirstName" value="" size="30" />
<br />
Last Name:<input type="text" name="LastName" id="LastName" value="" size="30" />
<br />
Job Title:<input type="text" name="JobTitle" id="JobTitle" value="" size="30" />
<br />
Phone:<input type="text" name="Phone" id="Phone" value="" size="12" />
<br />
Fax:<input type="text" name="Fax" id="Fax" value="" size="12" />
<br />
<input type="button" name="submit" value="save" onclick="insertEmployee();">
</form>
<div id="EmployeeList"></div> //placeholder div

Notice how there is no method or action in the form tag? Both of these will be taken care of by the JavaScript.

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All in all, I'd have to say I had a very pleasant experience using AJAX for the first time. The most difficult aspect of working with AJAX, was learning how to implement it. Once I found the right documentation, it was relatively smooth sailing.

Getting Started

First off, you should download an AJAX library. I recommend the Prototype javascript library. What is prototype.js anyway?

Prototype is a JavaScript framework that aims to ease development of dynamic web applications. Featuring a unique, easy-to-use toolkit for class-driven development and the nicest AJAX library around, Prototype is quickly becoming the codebase of choice for web application developers everywhere.

Basically, a guy named Sam Stephenson spent, I'm sure, an inordinate amount of time writing this great javascript file in order to make life easier on all of us. Using this file makes writing your AJAX code much easier. As mentioned earlier, the hardest part about getting started was finding documentation. So, in order to make it simpler for you, I'm going to include links to the documentation that I used to get started.

• Developer Notes for prototype.js - This documentation was exactly what I needed, and could quite possibly be the only thing you'll need. It contains some really great examples in the beginning of the document, and the contains more detailed information later on. After reading the first few paragraphs, I was able to get started, and then used the rest of the document for reference (this part of the document conveniently happens to be named "Reference for Prototype.js") haha.
• Working With Events In Prototype - How to use prototype with Keystrokes, Mouse Clicks, Mouse Hovers, etc.
• Eas y Ajax with Prototype

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Want to create a table that contains rows of alternating color? This is a little tutorial dedicated to showing you how. I've also added a third color to the mix. This will be used as a highlighting tool when the user mouses over a row. Let's start by having a look at the XHTML and ColdFusion code.
XHTML and ColdFusion:

<table>
<cfoutput query="EmployeeList">
<cfset rowid = "#EmployeeList.EmployeeID#">
  <tr class="#IIF(CurrentRow MOD 2, DE('dark'), DE('light'))#" id="#rowid#" onmouseover="changeBgcolor('#rowid#','rollovercolor');" onmouseout="changeBgcolor('#rowid#','#IIF(CurrentRow MOD 2, DE('dark'), DE('light'))#');">
    <td>
    ...
    </td>
  </tr>
</cfoutput>
</table>

Since the main idea here is to alternate the colors between rows, the key set of code from the above example is the following: currentrow MOD 2. What in the heck does this mean?

ColdFusion offers a modulus function (MOD) that returns the remainder (modulus) after a number is divided by a divisor; for example,10 MOD 3 is 1. -- livedocs.macromedia.com

Since even numbers divided by the number 2 will divide evenly (i.e. no remainder), and odd numbers when divided by 2 will not, we use CurrentRow MOD 2.

The CurrentRow variable is one of a few variables that ColdFusion automatically exposes that provide information about the query. These variables are often called query variables. -- livedocs.macromedia.com

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