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AJAX can be used for interactive communication
with an XML file.
AJAX XML Example
In the AJAX example below we will demonstrate how a web page
can fetch information from an XML file using AJAX technology.
Select a CD in the 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>
<p>
<div id="txtHint"><b>CD info will be listed here.</b></div>
</p>
</body>
</html>
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As you can see it is just a simple HTML form with a simple
drop down box called "cds".
The paragraph below the form contains a div called "txtHint".
The div is 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 JavaScript code is listed below.
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 ("Browser does not support HTTP Request")
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 || xmlHttp.readyState=="complete")
{
document.getElementById("txtHint").innerHTML=xmlHttp.responseText
}
}
function GetXmlHttpObject()
{
var objXMLHttp=null
if (window.XMLHttpRequest)
{
objXMLHttp=new XMLHttpRequest()
}
else if (window.ActiveXObject)
{
objXMLHttp=new ActiveXObject("Microsoft.XMLHTTP")
}
return objXMLHttp
}
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The AJAX Server Page
The server paged called by the JavaScript, is a simple 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.
The code runs a query against an XML file and returns the
result as HTML:
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
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