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JavaScript to load data from server
Web2 and caching example from a Well House Consultants training course
More on Web2 and caching [link]
Source code: ajax123.html Module: H307
<html>
<head>
<title>Steps towards AJAX in your web page</title>
<style>
#result { background-color: #DDDDFF;}
</style>
<script type=text/javascript language=javascript>
<!-- Hide Javascript on old browsers
function aboutlang(current) {
var lang = current.options[current.selectedIndex].value;
if (lang != "") {
document.getElementById("result").innerHTML = "Fetching " + lang;
var rqo = new XMLHttpRequest();
var qs = encodeURIComponent(lang);
var qry = "ajaxcode.php?towhich=" + qs;
rqo.open('GET',qry,false);
rqo.send(null);
document.getElementById("result").innerHTML =
rqo.responseText;
return false;
}
}
-->
</script>
</head>
<body>
<h1>Towards Ajax</h1>
<b>Have your server side HTML page interact with the server</b><hr />
<form>Please select a programming language
<select onChange="aboutlang(this)">
<option value="None">------</option>
<option value="Perl">Perl</option>
<option value="PHP">PHP</option>
<option value="Python">Python</option>
</select>
<input type="submit" value="Reload page / Reset"/>
</form>
<p id="result">This text initially loaded with page<br /><br />
<b>When you make a selection, the answer comes here</b></p>
<hr />
Ajax stands for "Asynchronous Javascript and XML" ... and this demonstration
is headed <i>toward</i> Ajax.<br /><br />
Using Ajax, a suitable browser can ask a server for dynamic information
to be filled in to an existing page, without the need to retransmit the
whole page - and in this example, we're calling up a server to replace the
text in the light blue box just above whenever a selection element on the
form is completed.<br /><br />
Why do I say "towards" Ajax rather than calling it "Ajax"?<br />
• In this easy example, I have NOT gone asynchronous - in other
words, the page is waiting for the response from the server within
the Javascript rather than setting up an event handler for later<br />
• The response isn't XML data in this case ... it's just a
chunk of HTML!<br /><br />
In this simple example too, we have not checked within our JavaScript as
to the make / version of the browser, so if it's used with a non
compliant browser it will fail silently.
</body>
</html>
Learn about this subject
This module and example are covered on our public PHP Techniques course. If you have a group of
three or more trainees who need to learn the subject, we can also arrange a
private or on site course for you.
Books covering this topic
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covering PHP are listed here and when you've selected a
relevant book we'll link you on to Amazon to order.
Other Examples
This example comes from our "Web2 and caching" training module. You'll find a description of the topic and some
other closely related examples on the "Web2 and caching" module index page.
Full description of the source code
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on which you'll be given a full set of training notes.
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