Asynchronous Requests with JavaScript and Ajax

An anonymous reader writes "I rarely read an entire article about a single object, especially one that is this simple. However, you will use this object over and over again in each page and application that you write that uses Ajax. This article shows you how to create XMLHttpRequest instances in a cross-browser way, construct and send requests, and respond to the server."

Comments

Re:IBM articles; Security with Javascript

[Jasin Natael]

Well, graceful degradation is nice, but...

I think users who are disabling JavaScript are already doing themselves more harm than good. There are some genuinely good dynamic interfaces out there, and compared to the time and bandwidth savings they'll get by using them properly, the time required to install FireFox or a popup/ad blocker is negligible.

At least for intranet and company sites, there's a genuine demand for functionality that it's impossible to expose without full Javascript support. Consider a drag-and-drop interface where customer orders appear on the left-hand side, and the line items can be organized into a grid of dates and production stations (a piece of machinery or a particular set of workers) via drag-and-drop. I have a working AJAX app that does this, but I can't think how such an application would be useful in the absence of JavaScript. It would require literally hundreds of pageloads and a metric ton of typing (remember: No Javascript = No Calendar Picker) to do any meaningful analysis and manipulation, and the very act of using it would destroy the user's workflow/concentration, rendering the application less useful than the scrawled paper notes it replaces.

This is the direction the web is moving. There are a lot of consumer applications that would benefit from taking a more dynamic approach, especially when you combine the intuitiveness of drag and drop with the live feedback made possible by XMLHTTPRequest. I think that coddling to users without JavaScript is holding them back, as well as creating a lot of useless "busy-work" for web designers and developers.

Jasin Natael

overriding the constructor

[ydnar]

With JavaScript, the object that is returned by the newoperator is the return value of the constructor. Which means you can set/override pretty much any object/property with a pseudo-constructor that returns any arbitrary object (class).

Adding XMLHttpRequest to Internet Explorer:

if( typeof window.XMLHttpRequest == "undefined" ) {
    window.XMLHttpRequest = function() {
        var types = [
            "Microsoft.XMLHTTP",
            "MSXML2.XMLHTTP.5.0",
            "MSXML2.XMLHTTP.4.0",
            "MSXML2.XMLHTTP.3.0",
            "MSXML2.XMLHTTP"
        ];

        for( var i = 0; i < types.length; i++ ) {
            try {
                return new ActiveXObject( types[ i ] );
            } catch( e ) {}
        }

        return undefined;
    }
}

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