Passing js callbacks for generic action | Action<T>

[FreakTheMighty]

I would like to pass a callback into a method with a generic definition but can't figure out how.

In JS I have

    marker
        .Clicked
        .Subscribe(function(){log('called')});

Which results in this error:

JavaScriptException: No public methods with the specified arguments were found.
Function <anonymous>:11:5
<anonymous>:11:5

Subscribe has a generic definition like this.

public static IDisposable Subscribe<T>(this IObservable<T> source, Action<T> onNext)

How does one go about exposing method like this? Thanks in advance for the advice.