Non-extensibility of Typed Arrays

Allen Wirfs-Brock allen at
Tue Aug 27 09:43:28 PDT 2013

On Aug 27, 2013, at 9:26 AM, Domenic Denicola wrote:

> I am not aware of all the nuances of the discussion, but as a developer I would find the behavior for numeric expandos confusing. For a typed array of length 1024, setting `ta[1023]` would do something completely different from setting `ta[1024]`. Unlike normal arrays, setting `ta[1024]` would not change `ta.length`, and presumably `ta[1024]` would not be exposed by the various iteration facilities.
> I would much rather received a loud error (in strict mode), which will either alert me to my code being weird, or possibly to my code committing an off-by-one error.

Integer numeric expandos on TypedArrays (eg, outside the range 0..length-1) are disallowed by the ES6 spec. in a manner that is independent of the[[Extensible]] internal property.  The discussion at the meeting was about non-numeric expandos such as 'foo'.


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