Head Rush Ajax

you’re on your way 4

37

next generation applications

You’ve uncovered the trickiest part of

asynchronous web programming: if

asynchronous code doesn’t wait around for

a response from the server, how do we use

that response? And where does the server’s

response go in the rst place?

You already know about web pages,

which can use event handlers to call

JavaScript functions. And you’ve seen

how asynchronous JavaScript can make

requests to a web server. To complete the

asynchronous picture, though, there’s

another important piece of the puzzle...

Where does the response go?

So if getBoardsSold() nishes running

before the server responds, where does

the response go? And how can we make sure

that updatePage() runs when the server’s

nished with our request?

Remember, getBoardsSold() makes

an asynchronous request. That means that

the JavaScript doesn’t wait around for an

answer from the server.

In fact, the getBoardsSold() function

will probably nish running before the

getUpdatedBoardSales-ajax.

php script even has a chance to nish

processing your request.

Ajax is asynchronous JavaScript

I think we should call the updatePage()

function at the end of getBoardsSold().

Then updatePage() can get the response

from the server, right?

function getBoardsSold() {

createRequest();

var url =

“getUpdatedBoardSales-ajax.php”;

request.open(“GET”, url, true);

request.send(null);

updatePage();

}

This won’t ...