Creating an autocomplete form field historically has not been a trivial matter and would require an indepth knowledge of JavaScript and CSS. However, the task is made far more simple when using one of the many freely-available JavaScript libraries. In this post I will show you how to implement the jQuery Autocomplete created by Dylan Verheul.

The Goal

Allow the user to type a few characters into a standard form text input field and to automatically provide suggestions from which the user can select.

Prerequisites

1. The latest copy of jQuery
2. A basic understanding of JavaScript
3. A server-side script that can respond to the AJAX request, in our case ColdFusion

Demo

The demo will specifically look at a simple form text input field, which takes a country name.

See the demo, and others, in action

How It Works

Once the user begins to type into the form text input field, the jQuery autocomplete is activated. After a set time interval, a list of items is displayed below the input field. The user can select these with either the arrow keys or mouse.

The Code

There are three parts to this demo:

1. The page’s HTML.
2. The server-side code to produce the dynamic page (i.e. to load the autocomplete div when the user types something into the input field).
3. The jQuery & JavaScript.

HTML Form

<h3>Example 1.: Country Lookup</h3>
<p>Using <abbr title="Asynchronous JavaScript and XML">AJAX</abbr> to interrogate the database.</p>
<p>Example data: Australia, Bulgaria, United Kingdom</p>
<form name="frmAutoCompleteCountry" id="frmAutoCompleteCountry" action="#" method="post">
<p>
<label for="country">Country</label>
<input type="text" name="country" id="country" />
</p>
</form>
<p>NB. If you have <a href="http://getfirebug.com/" title="Get Firebug">Firebug</a> installed you will be able to view the <abbr title="Asynchronous JavaScript and XML">AJAX</abbr> call.</p>

ColdFusion

This is a simple example, using a database to return a list of country names that match the characters the user has input. You could expand this and return a JSON data structure.

<cfsetting enablecfoutputonly="true">
<cfquery name="qryGetCountry" datasource="myDatasource">
SELECT countryName
FROM Country
WHERE countryName LIKE <cfqueryparam value="#URL.q#%" cfsqltype="cf_sql_varchar" />
</cfquery>
<cfoutput query="qryGetCountry">
#qryGetCountry.countryName##chr(10)#
</cfoutput>

JavaScript

The JavaScript will attach itself after the document is ready, i.e. after the page has loaded. Each time the text input field, with the ID of country, is changed, the autocomplete event is fired. This makes a call to the ColdFusion page, which returns a list of matched items.

<script type="text/javascript" src="jquery-1.2.6.min.js"></script>
<script type="text/javascript" src="jquery.autocomplete.js"></script>
<link type="text/css" href="autocomplete.css" rel="stylesheet" media="screen" />
<script type="text/javascript">
$(document).ready(function() {
	$("#country").autocomplete(
		"country.cfm",
		{
			minChars:2,
			delay:200,
			autoFill:false,
			matchSubset:false,
			matchContains:1,
			cacheLength:10,
			selectOnly:1
		}
	);
);
</script>

Where To Take It Next

JSON

The above example only shows a simple text list, separated by carriage returns. It is more preferable to use JSON.

Unobtrusive JavaScript

As with any page that is loaded with JavaScript and AJAX functionality, it should work without JavaScript.

To achieve this with the above tutorial, you will need to replace the jQuery autocomplete functionality with an ‘interim’ page that allows a user to select from a list of items, effectively turning the input field into a simple search interface. Of course, all other form field information would need to be retained between pages.

Download The Code

The example code can be downloaded from the demo page. Included are ColdFusion and PHP examples.

For many web developers, whenever JavaScript is mentioned it provokes a rye smile; JavaScript is one of those programming languages that is rather avoided than embraced. This is not the fault of the language itself, but rather the browsers. A few years ago, the landscape of client-side scripting was a bleak scene. Browser inconsistencies, particularly with the dominant Internet Explorer, implementation bugs and numerous target platforms made developing client-side JavaScript a tricky undertaking.

To the consternation of these same developers, the landscape changed and Web 2.0 hit the mainstream. Almost overnight, every website on the internet wanted to use or was using AJAX. Marketers joined the bandwaggon and every feature requested had to involve something dynamic and revolutionary. Thus JavaScript development quickly hit the forefront of peoples minds and became as important as any server-side technology available at the time.

Over the next few blog posts, I will be using the popular frameworks jQuery, Yahoo! User Interface Library (YUI), ExtJS and Adobe’s Spry with ColdFusion to demonstrate various techniques, such as autocomplete and form validation.