Rx.Observable.prototype.lastOrDefault([predicate], [defaultValue], [thisArg])Returns the last element of an observable sequence that satisfies the condition in the predicate if specified, else the last element.
predicate (Function): A predicate function to evaluate for elements in the source sequence. The callback is called with the following information:
[defaultValue] (Any): The default value if no such element exists. If not specified, defaults to null.[thisArg] (Any): Object to use as this when executing the predicate.(Observable): Sequence containing the last element in the observable sequence that satisfies the condition in the predicate.