BEST WEB HOSTING

AJAX Basic

AJAX HOME
AJAX Intro
AJAX Request
AJAX Example
AJAX Browsers
AJAX XMLHttpRequest
AJAX Server
AJAX Server Script

AJAX Advanced

AJAX Suggest
AJAX Source
AJAX Database
AJAX XML File
AJAX ResponseXML

AJAX Examples

AJAX XML Example

« Previous

Next Chapter »

AJAX can be used for interactive communication with an XML file.

AJAX XML example

The following example will demonstrate how a web page can fetch information from an XML file with AJAX technology.

Select a cd in the drop-down box below:

CD info will be listed here...

AJAX example explained

The example above contains a simple HTML form and a link to a JavaScript:

<html>
<head>
<script src="selectcd.js"></script>
</head>

<body>

<form>
Select a CD:
<select name="cds" onchange="showCD(this.value)">
<option value="Bob Dylan">Bob Dylan</option>
<option value="Bonnie Tyler">Bonnie Tyler</option>
<option value="Dolly Parton">Dolly Parton</option>
</select>
</form>

<div id="txtHint"><b>CD info will be listed here.</b></div>

</body>
</html>

As you can see it is just a simple HTML form with a simple drop down box called "cds".

The <div> below the form will be used as a placeholder for info retrieved from the web server.

When the user selects data, a function called "showCD" is executed. The execution of the function is triggered by the "onchange" event. In other words: Each time the user change the value in the drop down box, the function showCD is called.

The AJAX JavaScript

This is the JavaScript code stored in the file "selectcd.js":

var xmlhttp

function showCD(str)
{
xmlhttp=GetXmlHttpObject();
if (xmlhttp==null)
{
alert ("Your browser does not support AJAX!");
return;
}
var url="getcd.asp";
url=url+"?q="+str;
url=url+"&sid="+Math.random();
xmlhttp.onreadystatechange=stateChanged;
xmlhttp.open("GET",url,true);
xmlhttp.send(null);
}

function stateChanged()
{
if (xmlhttp.readyState==4)
{
document.getElementById("txtHint").innerHTML=xmlhttp.responseText;
}
}

function GetXmlHttpObject()
{
if (window.XMLHttpRequest)
{
// code for IE7+, Firefox, Chrome, Opera, Safari
return new XMLHttpRequest();
}
if (window.ActiveXObject)
{
// code for IE6, IE5
return new ActiveXObject("Microsoft.XMLHTTP");
}
return null;
}

The AJAX server page

The server page called by the JavaScript above, is an ASP file called "getcd.asp".

The page is written in VBScript for an Internet Information Server (IIS). It could easily be rewritten in PHP, or some other server language. Look at a corresponding example in PHP.

The code runs a query against an XML file and returns the result as HTML:

<%
response.expires=-1
q=request.querystring("q")

set xmlDoc=Server.CreateObject("Microsoft.XMLDOM")
xmlDoc.async="false"
xmlDoc.load(Server.MapPath("cd_catalog.xml"))

set nodes=xmlDoc.selectNodes("CATALOG/CD[ARTIST='" & q & "']")

for each x in nodes
for each y in x.childnodes
    response.write("<b>" & y.nodename & ":</b> ")
    response.write(y.text)
    response.write("<br />")
next
next
%>

The XML file

The XML file used in the example is "cd_catalog.xml". This document contains a CD collection.