Forum: Rails Spinoffs (closed, excessive spam) JSONP & Prototype.js

Hi list,

I've been looking for a JSONP implementation in Prototype, but can't
seem to find any yet. I came across something from a guy called Cody
Swann, but that didn't seem to work, and his website seems to have
disappeared. I tried to come up with a nice, integrated way to do it
myself, but I'm not sure that it's possible to use the default
Prototype Ajax way of doing things. Does anyone have something ready
to go, or can someone give me some pointers on how to best implement
it?

Cheers,
Ron Derksen

All JSONP is, is an endpoint that returns javascript that is a call to a
named function on your page, usually passing the resultant processed 
data as
a JSON parameter to said function. Some JSONP endpoints will have a 
fixed
name for that callback function, and some allow you to specify the name 
of
that function in your request parameters (usually via the query string 
since
JSONP is really designed for consumption via script tags, not Ajax).

There is nothing special you have to do on the client side other than 
have a
named function available (which again should match what the JSONP 
endpoint
is returning, or what you pass in to a configurable JSONP endpoint), and
allow your XHR layer to eval javascript (which Prototype does; see:
http://www.prototypejs.org/api/ajax/options).

If you're consuming a JSONP endpoint with Ajax, though, you're kind of
defeating one of the main purposes of JSONP. XHR, of course, requires 
that
you follow SOP (same origin policy), which means the XHR calls need to 
go to
the same domain as the current page. JSONP is really designed to be 
consumed
via script tags, thus is a cross domain scripting method primarily. If
you're building the backend yourself and aren't building a public 
service
API where you want to enable people to use script tags to make calls 
cross
domain... then for all intents and purposes you really don't need JSONP.

So anyway, the answer is you don't need to do anything special, just 
have a
named function available (at the global level) in your page, that the
returned javascript can call into.


On 6/17/08, Ron Derksen <chevalric@gmail.com> wrote:
> to go, or can someone give me some pointers on how to best implement
> it?
>
> Cheers,
>
> Ron Derksen
> >
>


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I've been playing with JSONP some time ago. Take a look at:
http://github.com/kangax/protolicious/tree/master/...

- kangax