I don't know, but I would suspect it's still the case, because doing anything else would require a lot of analysis of the code's behavior. In order to safely me

I don't know, but I would suspect it's still the case, because doing anything else would require a lot of analysis of the code's behavior. In order to safely merge all those definitions into one, the engine would have to know: * That the function in question never accesses anything in its closure that could be different for each construction * That hasOwnProperty() is never called on the object to check which way the method is declared (alternatively, remember that it had done this optimization, and spoof the return value) * That the function is never used as a constructor. Otherwise, Person could update sayHi's prototype and wind up changing its effects for all Persons, where it was supposed to create a customized inner class. And if you think any of these are easy, remember that you can get a pointer to that function via the following: var a = 'say', b = 'hi' var sayHi = (new Person)[a + b]