Function js::jsapi::JS_ObjectIsFunction

pub unsafe extern "C" fn JS_ObjectIsFunction(
    cx: *mut JSContext, 
    obj: *mut JSObject
) -> bool

Infallible predicate to test whether obj is a function object (faster than comparing obj's class name to "Function", but equivalent unless someone has overwritten the "Function" identifier with a different constructor and then created instances using that constructor that might be passed in as obj).