So according to this, it isn't possible. But I call bullshit, because the jQuery object, for instance, is able to be called as an object with member functions (jQuery.cookie()), but also as a function itself (jQuery('my_selector')).
How can I achieve the same effect with my objects? Let's say that I want an object named foo in the window namespace, with a member function bar, but also a function named foo in the same window namespace as the foo object. After declaring such an object-function hybrid, I'll be able to make the following calls:
window.foo(arg);
window.foo.bar(arg);