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Re: "The this value" (Was: onclick=function(){obj.meth()})

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Stefan Weiss wrote:

> On 2012-02-20 23:04, Gene Wirchenko wrote:
>>      Advanced readers: "the this object" is awkward.  "this" with or
>> without the quotes is confusing.  Is there a better way to refer to
>> the this object in English text?
> 
> It is awkward. I still haven't found a good way to reduce the
> awkwardness in plain text. It's easier when you can use markup (<code>)
> or italics or a different color, but on Usenet? *shrugs* I use what
> seems appropriate at the moment. Some use "this", or |this|, or `this'.
> I think that as long as it's clear what we're talking about, we're okay.
> It's not our fault that it has °this° silly name...

One must also differentiate between the "`this' value" (in the 
specification) and the "value of `this'" (in program code).

> BTW, the specs always used to refer to it as "the this value", not "the
> this object".

Correct.

> IIRC, that's because in ES3 it is possible to set |this| to a type other
> than object.

I do not see how that could be possible.  While it is true that you can 
specify the `this' value as not being an object reference, the value of 
`this' in ECMAScript Ed. 3-conforming program code will *always* be a 
reference to an object [1].

> In ES5 (strict mode only?), |this| always has to be of type object.

Incorrect; rather the reverse is true.

In ECMAScript Edition 5 strict mode function calls or execution contexts, 
`this' only refers to an object (and therefore could be said to be of 
Type(…) "Object") if the function is called *explicitly* as the method or 
constructor of an object [2].  IOW, in any String prototype method `bar', 
for "foo".bar(), `this' is the primitive String value "foo", not a reference 
to the String object referred by new String("foo") that needed to be created 
to call the method in the first place.  [This affects primarily the result 
of the `typeof' operation, as if a primitive string value is used with a 
property accessor, it is being converted internally to a String instance 
anyway (so you still can use `this.trim()', but it is easier to tell string 
values apart, or so perhaps was the intention of Ecma TC39.]

Further, with strict mode calls, the `this' value /is/ the `undefined' value 
if the base value of the Reference of the call was `undefined' or `null' 
[3].  IOW, in the strict mode call bar() or strict mode function context of 
`bar' ("use strict" at the start of the function body), where `bar' is a 
property of the Global Object and `globalRef' is a reference to the Global 
Object, `this' will only refer to the Global Object if bar is called as 
globalRef.bar().  While `bar()' being resolved to `globalRef.bar()' will 
cause the `this' value /to be/ the `undefined' value.

Google V8 in Chromium 16.0.912.77 (Developer Build 118311 Linux) and V8 in 
18.0.1025.33 beta (Linux) are (apparently; tested only in the Script Console 
as yet) not conforming regarding the latter.

> I could be mistaken about the details, but I'm too lazy to look it up now
> (it's late, and the wine was good).

It would appear to be prudent if one, in good scientific tradition, 
refrained from making claims that one is unable or unwilling to 
substantiate.


PointedEars
___________
[1] ECMA-262 Edition 3 Final, section 10.2
[2] ECMA-262 5.1 Edition, sections 11.2.3, 13.2.1 and 10.4.3
[3] ibid.
-- 
Prototype.js was written by people who don't know javascript for people
who don't know javascript. People who don't know javascript are not
the best source of advice on designing systems that use javascript.
  -- Richard Cornford, cljs, <f806at$ail$1$8300dec7@news.demon.co.uk>

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Thread

onclick=function(){obj.meth()} Puzzled <scratching.head@example.com> - 2012-02-20 14:02 -0500
  Re: onclick=function(){obj.meth()} "Tom de Neef" <tdeneef@qolor.nl> - 2012-02-20 20:20 +0100
    Re: onclick=function(){obj.meth()} Jake Jarvis <pig_in_shoes@yahoo.com> - 2012-02-20 20:39 +0100
      Re: onclick=function(){obj.meth()} "Richard Cornford" <Richard@litotes.demon.co.uk> - 2012-02-21 00:34 +0000
        Re: onclick=function(){obj.meth()} Stefan Weiss <krewecherl@gmail.com> - 2012-02-21 02:13 +0100
          Re: onclick=function(){obj.meth()} Richard Cornford <Richard@litotes.demon.co.uk> - 2012-02-21 04:05 -0800
        Re: onclick=function(){obj.meth()} Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-02-21 12:47 +0100
          Re: onclick=function(){obj.meth()} John G Harris <john@nospam.demon.co.uk> - 2012-02-21 15:59 +0000
  Re: onclick=function(){obj.meth()} Stefan Weiss <krewecherl@gmail.com> - 2012-02-20 21:09 +0100
    Re: onclick=function(){obj.meth()} "Evertjan." <exjxw.hannivoort@interxnl.net> - 2012-02-20 20:29 +0000
      Re: onclick=function(){obj.meth()} Puzzled <scratching.head@example.com> - 2012-02-20 16:50 -0500
        Re: onclick=function(){obj.meth()} "Evertjan." <exjxw.hannivoort@interxnl.net> - 2012-02-21 11:33 +0000
    Re: onclick=function(){obj.meth()} Puzzled <scratching.head@example.com> - 2012-02-20 15:47 -0500
      Re: onclick=function(){obj.meth()} Jake Jarvis <pig_in_shoes@yahoo.com> - 2012-02-20 22:38 +0100
        Re: onclick=function(){obj.meth()} Puzzled <scratching.head@example.com> - 2012-02-20 17:12 -0500
      Re: onclick=function(){obj.meth()} Gene Wirchenko <genew@ocis.net> - 2012-02-20 14:04 -0800
        "The this value" (Was: onclick=function(){obj.meth()}) Stefan Weiss <krewecherl@gmail.com> - 2012-02-21 01:37 +0100
          Re: "The this value" (Was: onclick=function(){obj.meth()}) Gene Wirchenko <genew@ocis.net> - 2012-02-20 17:20 -0800
          Re: "The this value" (Was: onclick=function(){obj.meth()}) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-02-21 13:44 +0100
            Re: "The this value" (Was: onclick=function(){obj.meth()}) Stefan Weiss <krewecherl@gmail.com> - 2012-02-21 22:31 +0100
              Re: "The this value" (Was: onclick=function(){obj.meth()}) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-02-22 10:55 +0100
                Re: "The this value" (Was: onclick=function(){obj.meth()}) John G Harris <john@nospam.demon.co.uk> - 2012-02-22 15:58 +0000
        Re: onclick=function(){obj.meth()} "Richard Cornford" <Richard@litotes.demon.co.uk> - 2012-02-21 01:30 +0000
      Re: onclick=function(){obj.meth()} Scott Sauyet <scott.sauyet@gmail.com> - 2012-02-20 13:43 -0800
      Re: onclick=function(){obj.meth()} Stefan Weiss <krewecherl@gmail.com> - 2012-02-20 23:17 +0100
        Re: onclick=function(){obj.meth()} Puzzled <scratching.head@example.com> - 2012-02-20 17:48 -0500
          Re: onclick=function(){obj.meth()} Stefan Weiss <krewecherl@gmail.com> - 2012-02-21 00:57 +0100
          Re: onclick=function(){obj.meth()} "Richard Cornford" <Richard@litotes.demon.co.uk> - 2012-02-21 01:03 +0000
            Re: onclick=function(){obj.meth()} Gene Wirchenko <genew@ocis.net> - 2012-02-20 19:05 -0800
              Re: onclick=function(){obj.meth()} Richard Cornford <Richard@litotes.demon.co.uk> - 2012-02-21 04:14 -0800
                Re: onclick=function(){obj.meth()} Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-02-21 13:54 +0100
                Re: onclick=function(){obj.meth()} Gene Wirchenko <genew@ocis.net> - 2012-02-21 10:17 -0800
                Re: onclick=function(){obj.meth()} Scott Sauyet <scott.sauyet@gmail.com> - 2012-02-21 11:57 -0800
                Re: onclick=function(){obj.meth()} Gene Wirchenko <genew@ocis.net> - 2012-02-21 13:39 -0800
                Re: onclick=function(){obj.meth()} Scott Sauyet <scott.sauyet@gmail.com> - 2012-02-22 05:07 -0800
            Re: onclick=function(){obj.meth()} Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2012-02-21 12:58 +0100
        Re: onclick=function(){obj.meth()} "Richard Cornford" <Richard@litotes.demon.co.uk> - 2012-02-21 00:45 +0000
          Re: onclick=function(){obj.meth()} Stefan Weiss <krewecherl@gmail.com> - 2012-02-21 02:22 +0100
        Re: onclick=function(){obj.meth()} Puzzled <scratching.head@example.com> - 2012-02-21 08:12 -0500
          Re: onclick=function(){obj.meth()} Scott Sauyet <scott.sauyet@gmail.com> - 2012-02-21 11:14 -0800

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