This JavaScript client library allows you to make Facebook API calls from any web site and makes it easy to create Ajax Facebook applications. Since the library does not require any server-side code on your server, you can now create a Facebook application that can be hosted on any web site that serves static HTML. An application that uses this client library should be registered as an iframe type. This applies to either iframe Facebook apps that users access through the Facebook web site or apps that users access directly on the app’s own web sites. Almost all Facebook APIs are supported. The exceptions are:

• Photo upload API is not supported.
• profile_setFBML() can only set FBML on the current user’s profile.

Using this client library is easy. You just need to follow two steps:

• Download and save content of http://api.facebook.com/static/xd_receiver.htm somewhere on your web site. For example, you can use http://www.foo.com/xd_receiver.htm for a Facebook App that’s hosted on http://www.foo.com.
• Reference the Facebook JavaScript http://static.ak.facebook.com/js/api_lib/FacebookApi.debug.js in your HTML page.

Here is the sample code for getting the current user’s friends list.

<!-- Output area to show the output from Facebook API -->
<textarea style="width:500px;height:300px;" id="_traceTextBox"><
     /textarea>

<script src="http://static.ak.facebook.com/js/api_lib/FacebookApi.debug.js"
 type="text/javascript"></script>
<script type="text/javascript">
// Create an ApiClient object, passing app’s api key and
// a site relative url to xd_receiver.htm
var api = new FB.ApiClient('<insert_your_app_key_here', '/xd_receiver.htm', 
   null);
        
// require user to login
api.requireLogin(function(exception) {

    window.alert(“Current user id is “ + api.get_session().uid);
  
    // Get friends list  
    api.friends_get(function(result, exception) {
      Debug.dump(result, 'friendsResult from non-batch execution ');  
    });       
});
</script>

For more information, please visit http://wiki.developers.facebook.com/index.php/JavaScript_Client_Library.