Reverse Posts order (source: from 'Ionic-Feed' project)
...
...
constructor(public db: AngularFireDatabase) {
// Listen for new data on this subject
this.posts = db.list('/posts', {
query: {
orderByChild: "date"
}
}).map((array) => array.reverse()) as FirebaseListObservable<any[]>; // reverse the List order (descending) so that new posts are first
...
}