The Existential Operator

A Matías Quezada amatiasq at gmail.com
Tue May 20 02:55:53 PDT 2014


I think the current use of this operator will only make sense if the
operator interrupts the whole sentence so

    a?.b.c

Will be the same as

    a && a.b.c

And

    a?().b?.c?.d

Will be same as

    a && (x = a(), x.b && (x.b.c && x.b.c.d))

---
A. Matías Quezada
Senior Javascript Developer
amatiasq at gmail.com



2014-05-20 11:31 GMT+02:00 Claude Pache <claude.pache at gmail.com>:

> Le 20 mai 2014 à 05:50, Dmitry Soshnikov <dmitry.soshnikov at gmail.com> a
> écrit :
>
> > Hi,
> >
> > (I remember, I mentioned this couple of years ago, but not sure about
> whether it was considered, etc)
> >
> > Will the "Existential Operator" for properly accessors be something
> interesting to consider for ES7 spec? Currently CoffeeScript uses it well.
> >
> > ```js
> > var street = user.address?.street;
> > ```
> >
> > The `street` is either the value of the `user.address.street` if the
> `address` property exists (or even if it's an object), or `null` /
> `undefined` otherwise.
> >
> > This (roughly) to contrast to:
> >
> > ```js
> > var street = user.address && user.address.street;
> > ```
> >
> > (the chain can be longer in many cases).
> >
> > The same goes with methods:
> >
> > ```js
> > var score = user.getPlan?().value?.score;
> > ```
> >
> > If potentially it could be interesting for ES7, I'll be glad helping
> with the proposal, grammar and algorithm (unless it was considered
> previously, and decided that it's not for ES for some reason).
> >
> > P.S.: I tried to solve this issue using default values of destructuring
> assignment, but it doesn't help actually.
> >
> > Dmitry
>
> Question: What is the semantics of the following:
>
>         a?.b.c
>
> Is it the same thing as
>
>         (a?.b).c
>         (a && a.b).c
>
> or the same thing as:
>
>         a && a.b.c
>
> (For the sake of the argument, just ignore the distinction between "falsy"
> and "null/undefined".)
> If it is the second option, I fear that the semantics of the so-called
> "existential operator" is more complicated than just an "operator".
>
> —Claude
>
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