Facebook's JavaScript SDK provides a rich set of client-side functionality for accessing Facebook's server-side API calls. It can collaborate with any SDK like PHP, C#, Java, android, ios, etc
From the Facebook developer site:
The JavaScript SDK provides a rich set of client-side functionality for accessing Facebook's server-side API calls. These include all of the features of the REST API, Graph API, and Dialogs. Further, it provides a mechanism for rendering of the XFBML versions of our Social Plugins.
You will need an app id to initialize the SDK, which you can obtain from the Developer App.
For example usage, check out Facebook for Websites and the Authentication guide. We also have a JavaScript Test Console which allows you to test and debug common JavaScript SDK methods.
We recently updated the JavaScript SDK to support OAuth 2.0.
