Path: csiph.com!weretis.net!feeder4.news.weretis.net!news.mb-net.net!open-news-network.org!.POSTED!not-for-mail
From: Thomas 'PointedEars' Lahn <PointedEars@web.de>
Newsgroups: comp.lang.javascript
Subject: Re: x === x
Date: Wed, 31 May 2017 12:39:50 +0200
Organization: PointedEars Software (PES)
Lines: 37
Message-ID: <19437984.EfDdHjke4D@PointedEars.de>
References: <JavaScript-20170530123255@ram.dialup.fu-berlin.de> <874lw231ui.fsf@bsb.me.uk> <context-20170530144535@ram.dialup.fu-berlin.de> <2872662.aeNJFYEL58@PointedEars.de> <87inkh28sf.fsf@bsb.me.uk>
Reply-To: Thomas 'PointedEars' Lahn <cljs@PointedEars.de>
NNTP-Posting-Host: 47.229.197.178.dynamic.wless.zhbmb00p-cgnat.res.cust.swisscom.ch
Mime-Version: 1.0
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8Bit
X-Trace: gwaiyur.mb-net.net 1496227191 28845 178.197.229.47 (31 May 2017 10:39:51 GMT)
X-Complaints-To: abuse@open-news-network.org
NNTP-Posting-Date: Wed, 31 May 2017 10:39:51 +0000 (UTC)
User-Agent: KNode/4.14.2
X-Face: %i>XG-yXR'\"2P/C_aO%~;2o~?g0pPKmbOw^=NT`tprDEf++D.m7"}HW6.#=U:?2GGctkL,f89@H46O$ASoW&?s}.k+&.<b';Md8`dH6iqhT)6C^.Px|[=M@7=Ik[_w<%n1Up"LPQNu2m8|L!/3iby{-]A+#YE}Kl{Cw$\U!kD%K}\2jz"QQP6Uqr],./"?;=4v
Face: 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
Xref: csiph.com comp.lang.javascript:33448

Ben Bacarisse wrote:

> Thomas 'PointedEars' Lahn <PointedEars@web.de> writes:
>> Stefan Ram wrote:
>>> Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
>>>> What's wrong with {} === {}?
>>>   It depends on the context.
>> No, it does not.  “===” *makes* the (expression) context.
> 
> $ nodejs -c -e '[] === [];' && echo "ok"
> ok
> $ nodejs -c -e '{} === {};' && echo "ok"
> [eval]:1
> {} === {};
>    ^^^
> 
> SyntaxError: Unexpected token ===
> <snip trace-back>
> $ nodejs -c -e '({} === {});' && echo "ok"                        ✘
> ok

Fascinating.  I had tried in the Chrome DevTools Console, and there the 
trailing semicolon makes the difference:

| > {} === {}
| <- false
| {} === {};
| (x) Uncaught SyntaxError: Unexpected token ===

I assume that the explicit semicolon there is considered an /EmptyStatement/ 
that switches back to statement context.

-- 
PointedEars
FAQ: <http://PointedEars.de/faq> | <http://PointedEars.de/es-matrix>
<https://github.com/PointedEars> | <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2 | Please do not cc me./Bitte keine Kopien per E-Mail.