Datasheet

FIGURE 1.5

The original Ajax article

That gap is indeed closing, thanks to Ajax. So, according to the article, what does “Ajax” actually

stand for? It stands for Asynchronous JavaScript and XML. As you can begin to see from its name,

and as you can read in the Jesse James Garrett article, Ajax is really a collection of technologies.

The “asynchronous” part means that the browser isn’t going to wait for data to be returned from

the server, but can handle that data as it’s sent back, when it’s sent back. In other words, data trans-

fers take place behind the scenes, without making the browser pause and wait for something to

happen. That’s a crucial part of Ajax: You can handle data from the server when the server sends

you that data. You don’t have to put your whole application on hold until that data arrives. If you

had to wait for that data, your application would be synchronous; and with slow Internet connec-

tions, that could be a problem.

The JavaScript part of the term Ajax is also very important because that’s what makes Ajax happen

in the browser. Ajax relies on JavaScript in the browser to connect to the server and to handle the

data that the server sends back. All the Ajax applications you will develop in this book use

JavaScript to connect to the server behind the scenes, uploading and downloading data. And when

your data is downloaded, you can use JavaScript in the browser to handle that data, displaying it or

crunching it as appropriate.

What about the XML part of the term Ajax? As you probably know, XML has become the lingua

franca of the Web, providing a text-based way to send data back and forth across the Internet. The

reason XML has become so popular is that it is indeed text-based, which means that you can sling

XML around the Internet, because the Internet was designed to handle text-based documents (that

is, HTML). For that reason, Ajax applications are often written to handle data sent back from the

server using XML. In other words, when you contact the server, it’ll send data back to you as an

XML document.

Essential Ajax

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