Head Rush Ajax

133

duplication prohibited

The browser will always run your callback,

because that gives you a chance to respond to

whatever the server did to handle your request.

Since you’re using an asynchronous request, the

callback is the only way you have to write code that can

deal with a server’s response. To help you out with

dealing with that response, the browser gives you both the

state of your request, and the status of your request.

There’s a different between the state of your request, and

the status of the same request. Your request’s ready state

tells the browser what stage of processing the request is in:

initialization, processing, completed, etc.. But just because

a request is complete doesn’t mean that the request was

successful... that involves the status of the request.

A server reports any problems with a request by using a status

code. The status code indicates what happened during the request,

and whether things went as you intended. So even if a request

was completed, you still need to make sure the status code for the

request indicates that everything went OK.

OK, so I see how it’s getting to the server. But if

the server can’t nd the program in the request URL

to run, why does the browser still run our callback?

Shouldn’t it report an error or something?

The browser always runs your callback...

...and it did report an error.