@@toStringTag spoofing for null and undefined

[Mark S. Miller]

Argh. Meant getYear of course.

On Wed, Jan 21, 2015 at 6:04 PM, Mark S. Miller <erights at google.com> wrote:

> Not intentional. I forgot that getDate was Annex B.
>
>
> On Wed, Jan 21, 2015 at 6:01 PM, Allen Wirfs-Brock <allen at wirfs-brock.com>
> wrote:
>
>>
>> On Jan 21, 2015, at 2:09 PM, Mark S. Miller wrote:
>>
>> // old ES5 code
>>
>> function f(allegedDate) {
>>   if (({}).toString.call(allegedDate) === "[object Date]") {
>>     JSON.stringify(allegedDate); // "[]" impossible in ES5
>>     Array.isArray(allegedDate); // true impossible in ES5
>>     Date.prototype.getYear.call(allegedDate); // error impossible in ES5
>>   }
>> }
>>
>>
>> // new ES6 code
>>
>> const fakeDate = [];
>> const defProp = Object.defineProperty;
>> defProp(fakeDate, Symbol.toStringTag, { value: "[object Date]" });
>> f(fakeDate); // all ES5 impossible behaviors happen
>>
>>
>> not quite.  The last of your tests (getYear) will still fail because
>> fakeDate is not internally branded as a date.
>>
>> See
>> http://people.mozilla.org/~jorendorff/es6-draft.html#sec-date.prototype.getyear step
>> 1 and the definition of "this time value" in
>> http://people.mozilla.org/~jorendorff/es6-draft.html#sec-properties-of-the-date-prototype-object
>>
>>
>> (BTW, did you intentionally pick an Annex B Date method?)
>>
>> Allen
>>
>
>
>
> --
>     Cheers,
>     --MarkM
>



-- 
    Cheers,
    --MarkM
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