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-boun...@mozilla.org] On Behalf Of kdex Sent: Saturday, August 19, 2017 1:55 PM To: es-discuss@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 <k...@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@mozilla.org > > https://mail.mozilla.org/listinfo/es-discuss _______________________________________________ es-discuss mailing list es-discuss@mozilla.org https://mail.mozilla.org/listinfo/es-discuss
