Head Rush Ajax

54

Chapter 1

Right now, your updatePage() function assumes that the server is nished

when it runs... but that’s not the case! To understand what’s going on with your

request, it’s time to learn about ready states. Your request object has a ready

state that tells the browser quite a bit about what state the request is in.

Make sure the server is finished

function getBoardsSold() {

createRequest();

var url = “getUpdatedBoardSales-ajax.php”;

request.open(“GET”, url, true);

request.onreadystatechange = updatePage;

request.send(null);

}

This property sets

the function that the

browser should run every

time that the request’s

ready state changes.

updatePage()createRequest() getBoardsSold()

A ready

state

tells the

browser

what stage

a request

is in.

Do you remember the property you used in getBoardsSold() to tell

the browser what to do when the server sent back a response? Take a look

to refresh your memory:

Ready states are connected to your request

object’s onreadystatechange property

This property affects every ready state,

not just the one indicating that the

server is nished with a request.

Web Browser

Internet Explorer

Firefox

Opera

Safari

Mozilla

PHP script

Request

Response

1

2

3

4

Here, the connection is just

getting initialized.

Now the request is

being worked on...

The server’s almost nished

with the request now.

All done! The

server’s response is

ready to be used.

These are the request’s ready sta ...