Head Rush Ajax

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Chapter 2

60 Second Review

ß For Microsoft browsers, the Ajax request

object is ActiveXObject, using either

Msxml2.XMLHTTP or Microsoft.XMLHTTP

as the type of the object.

ß For non-Microsoft browsers, including

FireFox, Safari, and Opera, the Ajax request

object is XMLHttpRequest.

ß Static JavaScript is JavaScript that is not in

a function, and is run by the browser when it

loads your page.

ß You can use static JavaScript to make sure

certain pieces of code run before users start

working with your web page.

ß A request’s ready state indicates what

is happening with the request: whether

it’s being initialized, the server has been

contacted, the server is finished, etc.

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

server has finished processing the request,

and any response data is safe to use.

ß Every time a request’s ready state changes,

the callback function registered with the

request is run by the web browser.

ß You need to use the DOM to update the text

in HTML display elements like <div> and

<span>; you can use the value property

to set the text of form field elements like

<input> and <textarea>.

ß Make sure the ordering of your fields works

with your application’s JavaScript, and not

against it, to help avoid confusing your users.

ß You need to use a different request URL

for each request to work around caching

browsers like Opera and Internet Explorer.

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