Get facebook user ids from sent requests callback using batch requests

gistfile1.js

FB.ui(
{
	method: 'apprequests',
	title: SP.copy._('js_invite_title'),
	message: SP.copy._('js_invite_message')
},
function(response){
	if (!FB.Dialog._stack.length) $('#sp_overlay').hide();
	if (!response) return;
	var batchStack = [],
		batchStackPool = [],
		maximumBatchLength = 20; // currently number of batch requests is limited to 20

	for (var i = -1, length = response.request_ids.length; ++i < length;) {
		batchStack.push({
			'method': 'GET',
			'relative_url': response.request_ids[i]
		});

		if (batchStack.length === maximumBatchLength) {
			batchStackPool.push(batchStack);
			batchStack = [];
		};
	};

	if (batchStack.length) {
		batchStackPool.push(batchStack);
	};

	// loop through pool by maximumBatchLength
	while (batchStackPool.length > 0) {
		FB.api('/', 'POST', { batch: batchStackPool.shift() }, function(resp) {
			var sentUids = [];
			for (var i = -1, length = resp.length; ++i < length;) {
				sentUids.push(jQuery.parseJSON(resp[i].body).to.id);
			};
			SP.Ajax.request({
				method: '/index/save.requests',
				params: { uids: sentUids }
			});
			sentUids = [];
		});
	};
});