Facebook batch calls with JSONP - facebook

Question

As of 10.04.2012,
There is a short paragraph in the Facebook developer document for 'batch request' entitled: Batch calls with JSONP, which reads:
"The Batch API supports JSONP, just like the rest of the Graph API -
the JSONP callback function is specified using the 'callback' query string
or form post parameter."
I thought that meant you can also do a batch request using JSONP from Javascript (which will be a GET request, as JSONP works only as a GET request), so I tried that, with adding a 'batch' parameter (containing objects describing requests for batch as in the doc) to the query string. Response from FB server was:
Only POST is allowed for batch requests
So, questions:
1. What did they mean in that paragraph?
2. Is there a way to do an asynchronous batch request from Javascript?

Answer 1

I get the same. Sample code is
jQuery.support.cors = true;
var AjaxRequest = jQuery.ajax( {
url: "http://graph.facebook.com/",
type: "POST",
contentType: "application/x-www-form-urlencoded",
data: { "access_token": AccessToken, "batch": BatchRequest },
dataType: "jsonp",
error: function( jqXHR, textStatus, errorThrown ) {
... show error stuff
},
success: function( Return, textStatus, jqXHR ) {
showLog( "Return " + JSON.stringify( Return ) );
showLog( "textStatus " + textStatus );
showLog( "jqXHR " + JSON.stringify( jqXHR ) );
if ( Return.error ) {
... go away
}
else {
... use the data
}
}
} ); // eo ajax request
which gives
Return {"error":3,"error_description":"Only POST is allowed for batch requests"}
textStatus success
jqXHR {"readyState":4,"status":200,"statusText":"success"}
i.e. it successfully sends back an error message. JSONP translates the POST type to a GET, which Facebook doesn't support...
To answer qu.2 you can use FB.api to do asynchronous batch request in javascript. I was trying out JSONP because IE8 keeps hanging on the return from Facebook with FB.api.