JavaScript Remote Scripting: Processing XML Files - Putting the pieces together: listing the complete script
(Page 6 of 6 )
As I said before, below is the list of the whole script, including a few additional lines to run the program after the page has been loaded:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
<title>READING XML FILES WITH AJAX</title>
<script type="text/javascript">
// initialize XMLHttpRequest object
var xmlobj=null;
var data=new Array();
// send http request
function sendRequest(doc){
// check for existing requests
if(xmlobj!=null&&xmlobj.readyState!=0&&xmlobj.readyState!=4){
xmlobj.abort();
}
try{
// instantiate object for Mozilla, Nestcape, etc.
xmlobj=new XMLHttpRequest();
}
catch(e){
try{
// instantiate object for Internet Explorer
xmlobj=new ActiveXObject('Microsoft.XMLHTTP');
}
catch(e){
// Ajax is not supported by the browser
xmlobj=null;
return false;
}
}
// assign state handler
xmlobj.onreadystatechange=stateChecker;
// open socket connection
xmlobj.open('GET',doc,true);
// send GET request
xmlobj.send(null);
}
// check request status
function stateChecker(){
// if request is completed
if(xmlobj.readyState==4){
// if status == 200 display text file
if(xmlobj.status==200){
// create data container
createDataContainer();
// read XML data
data=xmlobj.responseXML.getElementsByTagName
('message');
// display XML data
displayData();
}
else{
alert('Failed to get response :'+ xmlobj.statusText);
}
}
}
// create data container
function createDataContainer(){
var div=document.getElementById('container');
if(div){return};
var div=document.createElement('div');
div.setAttribute('id','container');
document.getElementsByTagName('body')[0].appendChild(div);
}
// display data at a given time interval
function displayData(){
// reset data container
document.getElementById('container').innerHTML='';
var ul=document.createElement('ul');
for(var i=0;i<data.length;i++){
// create links
var li=document.createElement('li');
var a=document.createElement('a');
// assign 'href' attribute
a.setAttribute('href',data[i].getElementsByTagName('url')
[0].firstChild.nodeValue);
// add link labels
a.appendChild(document.createTextNode(data
[i].getElementsByTagName('title')[0].firstChild.nodeValue));
li.appendChild(a);
ul.appendChild(li);
}
document.getElementById('container').appendChild(ul);
// update headlines each 1 hour
setTimeout("sendRequest('news.xml')",5*1000);
}
// execute program when page is loaded
window.onload=function(){
// check if browser is DOM compatible
if(document.getElementById&&document.
getElementsByTagName&&document.createElement){
// load XML file
sendRequest('news.xml');
}
}
</script>
<style type="text/css">
#container {
background: #eee;
padding: 5px;
border: 1px solid #000;
}
li {
margin-top: 5px;
}
a:link,a:visited {
font: bold 11px Tahoma, Arial, Helvetica, sans-serif;
color: #00f;
}
a:hover {
color: #f00;
}
</style>
</head>
<body>
</body>
</html>
To wrap up
That’s it for now. Throughout this second part of the series, you’ve hopefully learned how to use AJAX for reading and manipulating simple XML files, in order to implement a basic Web service. Certainly, the concepts that I illustrated at the very beginning imply a challenge for developing richer applications that use remote scripting to provide users with a more interactive experience.
The third tutorial of the series goes one step further with remote scripting, by explaining its implementation through the use of fully-standard DOM methods, without getting a single foot into AJAX technology. Want to know more? Just wait for the next part!
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