Axel Rauschmayer wrote:
I agree with Tom, "object" is the best choice if we are to avoid
extending typeof's codomain. If we choose to extend, then your best
case made above arguess for "symbol", not "string".
I’ve been wondering: instead of fixing typeof, wouldn’t it be simpler
to extend instanceof, by introducing new types:
- ReferenceType: to check whether a value is an object. Currently,
objects such as Object.create(null) and Object.prototype are objects
that are not instanceof Object.
This doesn't work with value objects, and anyway doesn't work by testing
proto-chain membership starting from RHS.prototype where RHS is the
constructor function.
- ValueType: for primitives and possibly future value objects.
- PrimitiveBoolean: for primitive booleans, same as typeof x ===
'boolean'
Again, we cannot inserte more prototypes on existing proto-chains.
- etc.
Should there ever be guards in the future, instanceof MyGuard would
also make sense.
If you are not using the proto-chain, then what? What's the underlying
theory for extending instanceof?
Compatibility concerns make this a non-starter, IMHO. We'd do better to
keep instanceof simple and extend typeof. IE already has extra typeof
results so developers have to beware.
/be
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