Array#indexOf and Array#lastIndexOf question

Allen Wirfs-Brock Allen.Wirfs-Brock at
Mon Jun 15 11:11:01 PDT 2009

Agreed...I'll fix it.

>-----Original Message-----
>From: es-discuss-bounces at [mailto:es-discuss-
>bounces at] On Behalf Of Brendan Eich
>Sent: Sunday, June 14, 2009 9:45 PM
>To: John-David Dalton
>Cc: es-discuss at
>Subject: Re: Array#indexOf and Array#lastIndexOf question
>On Jun 14, 2009, at 8:24 PM, John-David Dalton wrote:
>> I noticed that most Array methods perform [[HasProperty]] checks on
>> the index values.
>> Array#indexOf and Array#lastIndexOf do not. Firefox 3, Safari 4,
>> Chrome 2 all seem to check [[HasProperty]] for Array#indexOf and
>> lastIndexOf.
>> Is this an oversight on the draft or did the browser vendors miss
>> something ?
>Browser implementations, starting with Firerfox 1.5 / SpiderMonkey
>(JS1.6), preceded the spec, so the oversight is probably on TC39's
>part. I don't recall this coming up and a rationale for diverging from
>the de-facto standard being given.
>es-discuss mailing list
>es-discuss at

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