Ajax-client side JavaScript clarification

stormage · September 19th, 2010, 08:07 PM

Hey all!
I'm studying the Ajax in chapter 10.

in the TryItOut in page 352, we use HTML controls, and according to the book, and I quote: "you can see that the code you are going to write really
executes at the client".
I don't understand if we must work with HTML controls whenever we want to work with client side JavaScript that call web services??

One more thing, in page 352, there is this quote: "By referencing the service in the master page, it becomes available to all pages based on that master.
This also means that each page will download the JavaScript files needed to run this service."

what does it mean JavaScript files, I'm asking because all I saw is client side JavaScript code that invokes the web service, but not actual JavaScript files, that were downloaded.

10x u in advance

Imar · September 20th, 2010, 03:34 PM

Quote:

you can see that the code you are going to write really executes at the client".
I don't understand if we must work with HTML controls whenever we want to work with client side JavaScript that call web services??

No, that's not the case. You can also have server controls like the <asp:Button /> trigger web service calls. However, what I was demonstrating is that it works purely at the client, so you don't *have* to use server controls, but you could if you wanted to.

Quote:

what does it mean JavaScript files, I'm asking because all I saw is client side JavaScript code that invokes the web service, but not actual JavaScript files, that were downloaded.

TThere are; just look in the source of the page in the browser and you'll see a number of <script /> elements.[
QUOTE]
Here there are no events of any kind, so I guess that the fact that we registered a web service (which is accessible by client-side code ) to the web page, makes the JavaScript client code(the one that includes the HelloWorld function) at the highest priority to execute because both the JavaScript function and the web service method have the same name (HelloWorld).
[/QUOTE]
No, that's not how it works. Registering the web service just makes sure that the necessary scripts to talk to it are included (using JavaScript proxies). There's no such thing as a priority. You click the button which calls a JavaScript function which in turn talks to the web service using the JavaScript proxy class that ASP.NET has created and referenced for you when you registered the service.

Quote:

We know from earlier examples in the book, that when we have a Text Box and a Button, and we type something inside the Text Box and then click the Button, a postback occurs, and on the server the correct events are executed.

Yes, correct. But a button doesn't (typically) use JavaScript. A button is rendered as <input type="submit" ... /> which submits to the server by design.

Hope this helps,

Imar