Using Google`s Ajax Libraries API - Versioning with the Google API (
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True to form, versioning with the Google API is as simple as specifying which version of a particular JavaScript library should be downloaded when calling the pertinent “load()” method that you saw before.
To help you understand more clearly how this process works, below I have rewritten the Ajax-driven program that was built in the prior section, which now utilizes the versioning feature, to work specifically with Prototype 1.6. Here’s the corresponding code sample:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1" />
<title>Reading file contents with Prototype library (uses Google API)</title>
<style type="text/css">
body{
padding: 0;
margin: 0;
background: #fff;
}
h1{
font: bold 18pt Arial, Helvetica, sans-serif;
color: #000;
}
#filecontents{
width: 600px;
padding: 10px;
border: 1px solid #999;
font: normal 10pt Arial, Helvetica, sans-serif;
color: #000;
}
</style>
<script src="http://www.google.com/jsapi"></script>
<script>
// load Prototype library with Google API
google.load("prototype", "1.6");
// read file contents with Ajax
function readFileContents(){
// send http request
var ajaxobj=new Ajax.Request('read_file.php',{method: 'get',onComplete: displayFileContents,onFailure: displayError});
}
// display file contents
function displayFileContents(requestObj){
$('filecontents').innerHTML=requestObj.responseText;
}
// display error message
function displayError(requestObj){
$('filecontents').innerHTML='Error reading file contents!';
}
// initialize file reading application
function initializeApplication(){
// attach click handler to HTML button
Event.observe('btn','click',readFileContents);
}
google.setOnLoadCallback(initializeApplication);
</script>
</head>
<body>
<h1>Reading File Contents with Prototype library (uses Google API)</h1>
<p><input type="button" id="btn" value="Read File Now!" /></p>
<div id="filecontents"></div>
</body>
</html>
See how easy it is to work with a specific version of a JavaScript framework when using the Google API? As you can see, the only requirement of this process is to invoke the “load()” method by specifying the exact version of the library that must be served. That’s all.
With this concluding example I’ve finished this basic introduction to using Google’s JavaScript Libraries API. As usual, feel free to tweak all of the code samples developed in this article. This will give you a more intimate understanding of how to use this API when building your own client-side web applications.
Final thoughts
In this first chapter of the series, I explained how to use Google’s Ajax libraries API to download and work with the Prototype framework, instead of utilizing a local copy of it. It’s quite possible that the Google-based approach may appeal to you, particularly if your web hosting service has a heavy load, and you want to deliver your JavaScript files from Google's servers.
In the next part of the series, I’ll be discussing how to employ Google’s API for working with the jQuery JavaScript library. This can be helpful if you’re currently using this package for developing your client-side applications.
Don’t miss the upcoming tutorial!
