Head Rush Ajax

116

Chapter 2

Most Ajax apps start by running a JavaScript function based on

an event (like a phone number being entered in). The JavaScript

builds a request URL, and sends a request to that URL.

1

Your code makes a request to a web server

Web Browser

Internet Explorer

Firefox

Opera

Safari

Mozilla

PHP script

Here’s a look at

what happens

with the Boards

app, from

Chapter 1.

This request comes from the

browser, and not directly from

your JavaScript code.

Request Total

Boards Sold

Your code asks

that a request

be sent.

<script>

var request...

function foo()

{

...

}

</script>

getBoardsSold()

<?php

require(‘lib.php’);

function go() {

$myVar = ...

return ...

}

?>

Let’s take a closer look at exactly what browsers like Internet Explorer and Opera are

doing, and gure out why that creates trouble for our asynchronous apps.

When browsers cache request URLs...

When a response is sent back to the browser, the callback

function you specied is run. But, if the browser is caching

request URLs, it takes a note of the URL, and the answer from

the server, and saves those two values for later.

2

The server sends back a response

Web Browser

Internet Explorer

Firefox

Opera

Safari

Mozilla

PHP script

The browser also

stores the URL and

response so it can

use them later.

The server sends back an

answer to the request.

1643

<script>

var request...

function foo()

{

...

}

</script>

updatePage()

<?php

require(‘lib.php’);

function go() {

$myVar = ...