how facebook does cross domain ajax call?

Question

I am looking forward to create a javascript API that contains most of the functions that facebook Javascript API provides.

FB.api
FB.init
FB.logout
FB.getLoginStatus
FB.login
FB.ui

I can just embed script tag in remote website and need to do all the ajax calls from that page to my server. I am creating an architecture and needs someone help in finishing it with his/her excellent ideas.

Answer 1

You can also take a look at Cross Site XmlHttpRequest(CORS). From your question, it seems that you can control your server that will respond to the requests. In that case, you can tune the headers to receive requests and respond to cross domain requests.

Then, your embedded script will be able to talk to your server from any web page if you configure the request header in the requests that you make from your embedded script.

I like this method as it is extremely easy to implement. Watch out for browser support though!

Answer 2

Take a look at https://github.com/facebook/facebook-js-sdk/blob/deprecated/src/core/xd.js

They use a combination of rpc workarounds (with a relay file), Flash Local Connection and postMessage, whichever is supported by the browser.

Answer 3

They are using JSONP. It's widely used and is supported by javascript frameworks like JQuery.