Head Rush Ajax

60

Chapter 1

60 Second Review

ü Traditional web programming involves

making requests to a server, and getting

back a response, usually with updated data

wrapped up in a completely new HTML page.

ü Ajax apps use asynchronous JavaScript.

ü Ajax applications can make requests and get

responses without reloading an entire page.

ü Asynchronous JavaScript doesn’t wait on a

server to respond to a request. Users can

keep using a page, even while the server is

still working on the request.

ü Web browsers turn HTML and CSS into

pages you can see on your screen, and take

care of running any JavaScript in the page.

ü In Ajax applications, servers usually send

back just the data you request, without any

additional HTML markup and presentation.

ü You can use JavaScript to make both

synchronous and asynchronous requests to

a web server.

ü JavaScript offers several event handlers to

call JavaScript code when certain events

happen; onChange() and onClick() are two

common examples.

ü The browser always knows what ready state

a request is in, and makes that available to

your JavaScript functions.

ü You can have the browser run a JavaScript

function every time a request’s ready state

changes using the onreadystatechange

property in your request object.

ü When the ready state of a request is “4”, the

request has been processed, and the server

has a response ready.

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