> > I always disliked that some functions in ECMAScript 5 can be invoked as > either a function or a constructor. What would you want an entity Foo for > that can be invoked in two ways? E.g.: > new Foo(...) > Foo(...) >
Maybe Brendan can answer that one? : ) Seriously, though, it's a fair question. My first response is that since the Chapter 15 "classes" exhibit this behavior, we should be able to fully express it in a class syntax. But beyond that, how should we deal with this situation? We could make classes *not* implement [[Call]], but that would mean we'd have functions that didn't implement [[Call]], which is (AFAIK) truly novel and perhaps a little bizarre. I don't see that happening, but I could be wrong. So if [[Call]]/[[Construct]] duality is a fact, how *should* we deal with it? 1) Ignore the possibility of the constructor being [[Call]]ed. This is the typical response, because it's the easiest. It's also the most error-prone. 2) Use a best-effort approximation to detect a [[Call]] as in: https://github.com/joyent/node/blob/master/lib/buffer.js#L211-213 3) Separate the two behaviors into separate bodies, with a reasonable default for the [[Call]] operation. I think (3) makes the most sense. What do you think? kevin
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