Are objects values?

[Isiah Meadows]

Objects contain references to their fields, but they are always passed by
value. This is probably the distinction you're looking for.

On Sat, Aug 19, 2017, 16:32 Alex Kodat <alexkodat at gmail.com> wrote:

> While it does appear the that ECMAScript spec calls objects values, that
> seems pretty unintuitive to me. My intuition is that values are immutable
> (functions can and frequently do have properties added to them). The
> typical
> distinction seems to me between values and variables. If you set a variable
> to an object value how is it that the variable value changes when you
> change
> another variable? If, on the other hand, you view object values as
> references to object then changing one variable's value will never change
> another's which seems a nicer view of the world. But that was T.J.'s point,
> I think.
>
> Note that strings are also generally indistinguishable from immutable
> objects and are generally passed by reference under the covers but, because
> they're immutable, one can safely think of the value being the actual
> string
> rather than the reference. Numbers can be and sometimes are implemented as
> immutable objects too. Like V8 implements 32-bit signed integers as pure
> values and larger numbers are boxed (into hidden objects) double values.
>
> -----Original Message-----
> From: es-discuss [mailto:es-discuss-bounces at mozilla.org] On Behalf Of kdex
> Sent: Saturday, August 19, 2017 1:55 PM
> To: es-discuss at mozilla.org
> Subject: Re: Are objects values?
>
> I never claimed it was. I'm sure the notion of "value" that ECMAScript
> wants
> to convey is supposed to be something along the lines of "can be bound to
> an
> identifier".
>
> The semantics that are then defined over primitive/non-primitive values are
> a completely different matter.
>
> On Saturday, August 19, 2017 8:44:08 PM CEST Naveen Chawla wrote:
> > But references are also values. It's not a mutually exclusive thing
> >
> > On Sat, 19 Aug 2017, 11:32 p.m. kdex <kdex at kdex.de> wrote:
> > > Yes, objects/functions are values, but they are not *primitive* values.
> > >
> > > The current draft uses the phrasing "object value" several times.
> > >
> > > Section 4.3.3 explains that objects are "members of type Object",
> > > and a type is, by definition, a set of values. Therefore, objects
> > > must be values.
> > >
> > > On Saturday, August 19, 2017 7:34:45 PM CEST T.J. Crowder wrote:
> > > > I recently had an exchange which started out with my "correcting"
> > > > someone
> > > > who said "Functions are values" by saying "Function *references*
> > > > are values. Functions are objects." He/she replied that objects
> > > > are also values, and after much back and forth, cited [this part
> > > > of the JavaScript
> > > >
> > > > spec][1]:
> > > > > An ECMAScript *language type* corresponds to values that are
> > > > > directly
> > > >
> > > > manipulated by an ECMAScript programmer using the ECMAScript
> language.
> > >
> > > The
> > >
> > > > ECMAScript language types are Undefined, Null, Boolean, String,
> > > > Symbol, Number, and Object. An *ECMAScript language value* is a
> > > > value that is characterized by an ECMAScript language type.
> > > >
> > > > ...and said "So objects are values."
> > > >
> > > > Is he/she right? [Wikpedia][2] isn't much help, at least not to
> > > > me. I
> > >
> > > asked
> > >
> > > > a friend who, unlike me, did get comp sci theory at Uni, and he
> > > > said "...you're not wrong, but it's very Humpty Dumpty: When I use
> > > > a word, it means just what I choose it to mean -- neither more nor
> less."
> > > >
> > > > I've used the term "value" in explanations of variables,
> > > > properties, and function arguments and in particular when
> > > > explaining why `b = a` copies
> > >
> > > an
> > >
> > > > object reference, not an object, from `a` to `b`. (Saying the
> > > > *object
> > > > reference* is the value.) It's been an invaluable aid to helping
> > > > people "get" object references.
> > > >
> > > > I'd be very sorry to hear that I was misusing a term of art. But
> > > > I'd
> > >
> > > rather
> > >
> > > > know. :-)
> > > >
> > > > If I'm misusing "value," what should I use instead for that thing
> > > > that actually gets stored in memory? How to explain the `b = a`
> > > > thing with object references to beginners?
> > > >
> > > > This is slightly off-topic for the thread, but also not, as I
> > > > spend a lot of time explaining things to JavaScript beginners, and
> > > > the authors of the text being used to tell me I'm wrong are on
> > > > this list. :-)
> > > >
> > > > Thanks,
> > > >
> > > > -- T.J. Crowder
> > >
> > > > [1]:
> > > http://www.ecma-international.org/ecma-262/8.0/index.html#sec-ecmasc
> > > ript-l
> > > an>
> > > > guage-types [2]:
> > > > https://en.wikipedia.org/wiki/Value_(computer_science)
> > >
> > > _______________________________________________
> > > es-discuss mailing list
> > > es-discuss at mozilla.org
> > > https://mail.mozilla.org/listinfo/es-discuss
>
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