Le 07/07/2011 13:11, Tom Van Cutsem a écrit :
2011/7/6 Andreas Rossberg <[email protected]
<mailto:[email protected]>>
While putting together some test cases for Object.keys, I wondered: is
it intended that property names are always passed to traps as strings?
That is indeed the intent.
It seems like a reasonable assumption, but is not currently the case
everywhere (e.g. the default implementation for `keys' can violate
this assumption when passing names to this.getOwnPropertyDescriptor).
How so? The default implementation for the keys trap relies on the
return value of the getOwnPropertyNames() trap, whose return value is
coerced to an array of Strings.
The return value of the trap is. The return value of
this.getOwnPropertyNames isn't.
With a "pure" mapping from internal methods to trap, the trap call and
handler.trap (this.trap) are the same. However, with invariant
enforcement, they are different. Type coercion is a such an invariant
enforcement (that actually could be added to FixedHandler).
David
Cheers,
Tom
/Andreas
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