We've covered Ajax, so let's talk a little about remote scripting. You might think, "What's the big deal about Ajax?" I've already done the same thing with IFRAME. "In fact, we have used this method ourselves," he said. This is commonly referred to as Remote scripting (scripting), which many people think is just a patchwork. However, this does provide a mechanism to avoid page refreshes.
2.5.1 Remote Scripting Overview
Basically, a remote script is a type of remote procedure call. You can interact with the server like a normal Web application, but you don't need to refresh the entire page. Like Ajax, you can call any server-side technology to receive requests, process requests, and return a meaningful result. Just as there are many choices on the server side, the client also has many options for implementing remote scripting. You can embed Flash animations, Java applets, or ActiveX components in your application, and you can even use XML-RPC, but this approach is too complex, so unless you are experienced with this technique, this approach is not appropriate. The common practice of implementing remote scripting involves combining a script with an IFRAME (hidden or not hidden), and returning JavaScript to the server, which then runs the JavaScript in the browser.
Microsoft provides its own remote scripting solution, and is intelligently referred to as Microsoft Remote scripting (Microsoft Sqlremote Scripting,msrs). In this way, you can call a server script just like a local script. The Java applet is embedded in the page to communicate with the server, the. asp page is used to place server-side scripts and the. htm file manages the layout of the client. Microsoft's solution can be used in both Netscape and IE 4.0 and later, and can be invoked synchronously or asynchronously. However, this solution requires Java, which means that additional installation routines may be required, as well as Internet Information Services (IIS), which limits server-side selection.
Brent Ashley created two free cross-platform libraries for remote scripting. JSRs is a client-side JavaScript library that leverages DHTML to make remote calls to the server. JSRs can be used on a considerable number of operating systems and browsers. If you use some of the most popular server-side implementations (such as PHP, Python, and Perl CGI), JSRs can typically be installed and run on a Web site. Ashley provides JSRS for free and can also get the source code from his website (www.ashleyit.com/rs/main.htm).
If you think JSRs is too bulky, Ashley also creates Rslite, which uses cookies. Rslite is limited to a small amount of data and a single call, but most browsers provide support.
Examples of 2.5.2 remote scripts
For comparison, this shows you how to use an IFRAME to implement AJAX-like techniques. This is very simple, and we used to use this method in the past (before the advent of XMLHttpRequest). This example does not really call the server, just wants you to know how to implement a remote script using IFRAME.
This example includes two files: iframe.html (see Code Listing 2-2) and server.html (see Code Listing 2-3). The server.html simulates the response that should be returned from the server.
Code listings 2-2 iframe.html Files
<title>Example of remote scripting in an IFRAME</title>
<script type="text/javascript">
function handleResponse() {
alert('this function is called from server.html');
}
</script>
<body>
<iframe id="beforexhr"
name="beforexhr"
style="width:0px; height:0px; border: 0px"
src="blank.html"></iframe>
<a href="server.html" target="beforexhr">call the server</a>
</body>
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