fb-query-2-snippet.js

function getMostPopularForCourse(courseId, tag) {
    var questionsNode =
            tag ?
                ref.child('discussions').child('byCourseByTag').child(courseId).child(tag)
                : ref.child('discussions').child('byCourse').child(courseId);

    // create a query for the most popular messages on the server
    var query = questionsNode.orderByChild("voteSum")

    return $firebaseArray(query.limitToLast(pagingOptions.count));
}