Returns the first element of an observable sequence that satisfies the condition in the predicate, or a default value if no such element exists.
Function): A predicate function to evaluate for elements in the source sequence. The callback is called with the following information:
Any): The default value if no such element exists. If not specified, defaults to null.
Any): Object to use as
thiswhen executing the predicate.
Observable): An observable sequence that contains elements from the input sequence that satisfy the condition.