Head Rush Ajax

you’re on your way 4

55

next generation applications

function updatePage() {

if (request.readyState == 4) {

var newTotal = request.responseText;

var boardsSoldEl = document.getElementById(“boards-sold”);

var cashEl = document.getElementById(“cash”);

replaceText(boardsSoldEl, newTotal);

/* Figure out how much cash Katie has made */

...

/* Update the cash total on the web form */

...

}

}

Here’s

that code

you wrote

a few

pages back.

When the request object’s

readyState is set to 4, the

server is done with the request.

Don’t forget the closing bracket.

You already know that the browser will run your updatePage() function when it gets a response

from the server. But, there’s a twist: the browser actually runs updatePage() every time the ready

state changes, and not just when the server is nished sending back a response. Look at the diagram

on page 54 again, and notice that as the request is progressing, the ready state number changes.

It looks like when the server is nished with our request, the ready state is “4”, so we can check for

that number in our code. That way, we can make sure that we only try and update Katie’s report

when we know that the server has sent us back a response.

Checking for the right ready state

readyState is the property on the request

object that stores the current ready state.

This function

will get run

every time

the ready

state changes.

When the serv