Load XML contents to HTML websites dynamically
<p>Writing contents directly into HTML websites is less maintainable and extensible. Hence, contents are stored in XML files and loaded dynamically to structured HTML websites.</p><p>Please find out a detailed way to achieve the mentioned goal.</p>
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Using AJAX to load XML contents dynamically to XHTML websites
First we are going to create a standard HTML form with two input fields: Name and Time. The "Name" field will be filled out by the user, and the "Time" field will be filled out with AJAX.The HTML file will be named "testAjax.htm", and it looks like this (notice that the HTML form below has no submit button!):<html><body><form name="myForm">Name: <input type="text" name="username" />Time: <input type="text" name="time" /></form></body></html>The keystone of AJAX is the XMLHttpRequest object.All new browsers use the built-in JavaScript XMLHttpRequest object to create an XMLHttpRequest object (IE5 and IE6 uses an ActiveXObject).Let's update our "testAjax.htm" file with a JavaScript that creates an XMLHttpRequest object:<html><body><script type="text/javascript">function ajaxFunction(){var xmlhttp;if (window.XMLHttpRequest) { // code for IE7+, Firefox, Chrome, Opera, Safari xmlhttp=new XMLHttpRequest(); }else if (window.ActiveXObject) { // code for IE6, IE5 xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); }else { alert("Your browser does not support XMLHTTP!"); }}</script><form name="myForm">Name: <input type="text" name="username" />Time: <input type="text" name="time" /></form></body></html>Example explained1. Create a variable named xmlhttp to hold the XMLHttpRequest object.2. Try to create the XMLHttpRequest object with xmlhttp=new XMLHttpRequest().3. If that fails, try xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"). This is for IE6 and IE5.To send off a request to the server, we use the open() and send() methods.The open() method takes three arguments. The first argument defines which method to use when sending the request (GET or POST). The second argument specifies the URL of the server-side script. The third argument specifies that the request should be handled asynchronously.The send() method sends the request off to the server. If we assume that the HTML and ASP file are in the same directory, the code would be:xmlhttp.open("GET","time.asp",true);xmlhttp.send(null);Now we must decide when the AJAX function should be executed.We will let the function run "behind the scenes" when a user types something in the "Name" field:<form name="myForm">Name: <input type="text" name="username" onkeyup="ajaxFunction();" />Time: <input type="text" name="time" /></form>Our updated "testAjax.htm" file now looks like this:<html><body><script type="text/javascript">function ajaxFunction(){var xmlhttp;if (window.XMLHttpRequest) { // code for IE7+, Firefox, Chrome, Opera, Safari xmlhttp=new XMLHttpRequest(); }else { // code for IE6, IE5 xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); }xmlhttp.onreadystatechange=function(){if(xmlhttp.readyState==4) { document.myForm.time.value=xmlhttp.responseText; }}xmlhttp.open("GET","time.asp",true);xmlhttp.send(null);}</script><form name="myForm">Name: <input type="text" name="username" onkeyup="ajaxFunction();" />Time: <input type="text" name="time" /></form></body></html>Now we are going to create the server-side script that displays the current time.The responseText property (explained in the previous chapter) will store the data returned from the server. Here we want to send back the current time.The code in "time.asp" looks like this:<%response.expires=-1response.write(time)%>Note: The response.expires command sets how long time (in minutes) a page will be cached on a browser before it expires. If a user returns to the same page before it expires, the cached version is displayed. response.expires=-1 indicates that the page will never be cached.
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