I stand corrected on the creation aspect. Isiah Meadows On Aug 25, 2014 9:56 PM, "Brendan Eich" <[email protected]> wrote:
> Isiah Meadows wrote: > >> >> Cc the list... >> >> On Aug 25, 2014 6:06 PM, "Isiah Meadows" <[email protected] <mailto: >> [email protected]>> wrote: >> >> There really shouldn't be any sort of object construction needed >> to check types like this. `isa` may be better, anyways, but I >> still find that requirement to build and destroy an object to >> check somewhat counterproductive. >> >> > What object is built and destroyed? > > Note that for primitive types no wrapper need be created just to call a > method, in general for JIT-optimized code, and definitely for strict mode > code. > > Andrea gets what I'm talking about. Also, another (possibly >> separate) proposal would be to make cases like `"foo" instanceof >> String" === true` instead of their current behavior, throwing a >> TypeError. (I believe...I'm on a phone, not a PC where I can test. >> Correct me if I'm wrong.) >> >> > (Your phone doesn't have a browser with a console? :-P) > > js> "hi" instanceof String > false > js> 42 instanceof Number > false > js> false instanceof Boolean > false > > These are well-defined for instanceof, without throwing. Changing results > to true would be backward incompatible. > > ES4 had 'is' as a type-classifying operator: > > http://wiki.ecmascript.org/doku.php?id=proposals:is_as_to > http://wiki.ecmascript.org/doku.php?id=discussion:is_as_to > > It would be a mistake to define 'is' without defining the (unsound) type > system it depends on. This is a challenge, but TypeScript and other > close-to-ES6 languages have sallied forth. We need a detailed proposal. > > /be >
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