At Dojo, we're committed to making DHTML applications usable, both for authors and for users, and with a lot of help from our friends, particularly Aaron Boodman and Mark Anderson, we have come up with solutions to the usability problems outlined above. We're providing it in a single, easy to use API and a package that requires only two files to function. The dojo.io package provides portable code for XMLHTTP and other, more complicated, transport mechanisms. Additionally, the "transports" that plug into it each provide their own logic to make each of them easier to use.

Most of the magic of the dojo.io package is exposed through the bind() method. dojo.io.bind() is a generic asynchronous request API that wraps multiple transport layers (queues of iframes, XMLHTTP, mod_pubsub, LivePage, etc.). Dojo attempts to pick the best available transport for the request at hand, and in the provided package file, only XMLHTTP will ever be chosen since no other transports are rolled in. The API accepts a single anonymous object with known attributes of that object acting as function arguments. To make a request that returns raw text from a URL, you would call bind() like this:

dojo.io.bind({

    url: "http://foo.bar.com/sampleData.txt",

    load: function(type, data, evt){ /*do something w/ the data */ },

    mimetype: "text/plain"

});

That's all there is to it. You provide the location of the data you want to get and a callback function that you'd like to have called when you actually DO get the data. But what about if something goes wrong with the request? Just register an error handler too:

dojo.io.bind({

    url: "http://foo.bar.com/sampleData.txt",

    load: function(type, data, evt){ /*do something w/ the data */ },

    error: function(type, error){ /*do something w/ the error*/ },

    mimetype: "text/plain"

});