As a day-to-day user who was not using strict until recently (stubborn other team member for the loss), I can say that moving to strict was much more a "cleanup" experience than a "mode" experience, with only a few small exceptions:
1) Poison-pilling arguments.callee: some code on the internet (notably [1], but elsewhere too) uses this property. 2) Throw on `delete`ing non-configurables: unlike the other throw-on-doing-something-bad, `delete`ing non-configurable properties was something we actually did on purpose. E.g. using it to clear an "entry" in a "map", whether or not that entry was ever filled. (Cf. [2].) We never tried writing to a non-writable property, because that would cause bugs, but `delete`ing a property that doesn't exist was a common pattern. [1]: http://www.devthought.com/2011/12/22/a-string-is-not-an-error/ [2]: https://github.com/cjohansen/Sinon.JS/commit/80c38bd3e4b8813ab74ef27a4db3646e4778e31c --- Otherwise, it was just cleanup: we got to get rid of our global detector (`setInterval(compareWindowPropertiesToLastTimeYouChecked(), 1000)`), never missed `with` or evil-`eval`, and due to a V8 bug never had boxed `this` in the first place. We're using it transparently throughout the codebase, in fact, due to using an XHR+`eval` module loader that can insert the `"use strict"` pragma before `eval`ing. > -----Original Message----- > From: [email protected] [mailto:es-discuss- > [email protected]] On Behalf Of David Herman > Sent: Monday, April 23, 2012 19:11 > To: Brendan Eich > Cc: es-discuss > Subject: Re: A few arrow function specification issues > > On Apr 23, 2012, at 2:44 PM, Brendan Eich wrote: > > > Brendan Eich wrote: > >> Without arguments runtime semantic shifts, and with |this| lexical, > there aren't many strict mode changes left IIRC, and they are pretty edgy > edge cases. > > > > True enough, but I hang tough on wanting arrows to imply strictness. I > may be wrong but the edge cases cited so far (global variable creation by > assignment, 'with', direct eval injecting 'var' into its dynamic scope) > along with this |this|-boxing one are underwhelming. > > IMO, this decision hangs on whether we think strict mode can be thought > of as a "cleaning up" that will mostly just catch bugs, resulting in > failing faster but otherwise not changing program behavior significantly. > > POSITION "CLEANUP": If it's just a cleanup, then it makes sense to > introduce strict mode in a bunch of places in the language. It'll catch > bugs, and for the most part people won't have to think to themselves "is > this strict code?" > > POSITION "MODE": If it's something that is likely to change behavior in > meaningful ways other than failing faster, then it's something > programmers will have to be mindful of. In that case, having multiple > constructs that implicitly introduce strict mode imposes a burden on > programmers: they have to know which features are strict and which ones > aren't. > > Every fiber of my being screams MODE. Brendan argues CLEANUP based on the > rationale that the non-error semantic changes of strict mode are unlikely > edge cases. This is the strongest argument against MODE. I can't prove it > wrong, but it's a risky bet. If it turns out to be the case that in > practice you need to keep track of whether you're in strict mode, then > weak programmers who don't know better will end up with a confusing mess, > and strong programmers will prophylactically make sure to put their > entire programs in strict mode rather than memorize which subset of > syntaxes opt in. Since strong programmers have the option to do that > anyway even without multiple implicit opt-ins, why take the risk? > > Pascal^H^H^H^H^H^H Dave > > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
