Stricter "use strict"

Francisco Ferreira francisco.m.s.ferreira at
Tue Apr 16 02:29:34 PDT 2013

Just to clarify about the map[undefined] example. Yes I'm talking about the
regular object 'var foo = {}', I know this is a minor detail, but I assume
that whenever 'undefined' is set as a key (both for insertion and
retrieval). It's most likely because something wrong happened. I can't
imagine a logic that depends on setting foo[undefined] = 'something'. And
the developer should be warned about it either with a thrown runtime error
or with a console warning.

Thanks for the references, that pretty much clarifies what I had in mind.

On Tue, Apr 16, 2013 at 11:12 AM, David Bruant <bruant.d at> wrote:
>> Hi Francisco,
>> TC39 (which I'm not part of) agreed to not add more modes to ECMAScript.
>> They try to follow the "1JS" rule, that is there is only one language.
>> Among other things, this makes writing parsers and interpreters easier. I
>> think this all started at [1] (you don't need to read everything, but it
>> gives an idea).
>> Strict mode was necessary to fix big flaws of the language that needed to
>> be fixed and couldn't be without a mode, but that's as far as it went.
>> Based on the examples you gave, it seems you haven't pointed at major
>> language flaws that justify a new mode. More on that inline.
>> Le 16/04/2013 10:28, Francisco Ferreira a écrit :
>>  Stuff that pops my mind that "use strict" doesn't cover and that could
>>> be useful is:
>>> "use stricter";
>>>  - Enforces the use of ';' at the end of a line of code
>> Be careful, this can be a sensitive topic for some people and may end up
>> with flames :-) On that topic, I highly recommend Brendan Eich's article
>> [2] which among other things summarizes a drama that animated the JS
>> community.
>>   - Either force the usage of '===' instead of '==' or make '==' more
>>> type safe.
>> You might be interested in restrict mode [3]
>>   - Makes map[undefined] break or throw a warning
>> By "map", i assume you're referring to a regular object and not an ES6
>> map. What do you mean by "break" and "throw a warning"? Do you want a
>> runtime error to be thrown or this error to be caught by devtools?
>> As a developer, one thing you can do is at least build a tool (like
>> restrict mode) and add git/mercurial/svn per-commit hook to enforce that
>> your 2 first points are enforced. This way, when you and your team write
>> JavaScript, you can be guaranteed that semicolons are in and that no one
>> uses ==. I don't fully understand your 3rd point so I'm not sure a tool can
>> catch that, but my point is that by building tools yourself, you can
>> enforce the sublanguage of your choice in your projects.
>> David
>> [1]**pipermail/es-discuss/2011-**
>> December/019112.html<>
>> [2]**04/the-infernal-semicolon/<>
>> [3]
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