Re: why the ! operator can be used to determine a string is null?

From	Cezary Tomczyk <cezary.tomczyk@gmail.com>
Newsgroups	comp.lang.javascript
Subject	Re: why the ! operator can be used to determine a string is null?
Date	2017-08-10 09:10 +0200
Organization	csiph.com Internet News Service
Message-ID	<omh0u2$1quk$1@csiph.com> (permalink)
References	<omcm6a$rga$1@gioia.aioe.org> <1939054.irdbgypaU6@PointedEars.de> <e3a5d53f-250f-41b9-83a4-792d3c042966@googlegroups.com> <omedf0$3i$1@csiph.com> <11859138.uLZWGnKmhe@PointedEars.de>

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On 09/08/2017 11:32, Thomas 'PointedEars' Lahn wrote:
> Cezary Tomczyk wrote:
> 
>> On 09/08/2017 06:20, Julio Di Egidio wrote:
>>> On Tuesday, August 8, 2017 at 11:20:26 PM UTC+2, Thomas 'PointedEars'
>>> Lahn wrote:
>>>> Second, the function call `prompt()` is actually the method call
>>>> `window.prompt()` and should always be written so.
>>> Nah, that's just a bit of your misplaced dogmatism.
>>
>> That's not dogmatism, but a practical and good advice to use full
>> reference to a method. Time ago I wrote article about that:
>>
>> http://www.ctomczyk.pl/js-tip-always-use-full-reference/282/
> 
> Your solution to the problem looks suboptimal to me, though.  First you say
> 
> | // "global" represent "window" object in browsers
> 
> which, AISB, for
> 
>    (function (global) {
>      /* … */
>    }(this));
> 
> is questionable.  The ECMAScript 2016 Language Specification, clarifying
> previous Editions, only says in that regard:
> 
> ,-<http://www.ecma-international.org/ecma-262/7.0/>
> |
> | […]
> |
> | 4.1 Web Scripting
> |
> | A web browser provides an ECMAScript host environment for client-side
> | computation including, for instance, objects that represent windows,
> | menus, pop-ups, dialog boxes, text areas, anchors, frames, history,
> | cookies, and input/output. Further, the host environment provides a means
> | to attach scripting code to events such as change of focus, page and image
> | loading, unloading, error and abort, selection, form submission, and mouse
> | actions. Scripting code appears within the HTML and the displayed page is
> | a combination of user interface elements and fixed and computed text and
> | images. The scripting code is reactive to user interaction and there is no
> | need for a main program.
> |
> | A web server provides a different host environment for server-side
> | computation including objects representing requests, clients, and files;
> | and mechanisms to lock and share data. By using browser-side and server-
> | side scripting together, it is possible to distribute computation between
> | the client and server while providing a customized user interface for a
> | Web-based application.
> |
> | Each Web browser and server that supports ECMAScript supplies its own host
> | environment, completing the ECMAScript execution environment.
> 
> and
> 
> | 18 The Global Object
> |
> | […]
> | In addition to the properties defined in this specification the global
> | object may have additional host defined properties. This may include a
> | property whose value is the global object itself; for example, in the HTML
>                                                      ^^^^^^^^^^^
> | document object model the `window` property of the global object is the
> | global object itself.
> 
> The caveat here is that the first quoted section, being part of section
> “4 Overview”, which is not normative, and examples in general, are *not
> normative*.  *Many people misunderstand this* when referring to technical
> specifications, and ECMAScript in particular.
> 
> The *ECMAScript Language* Specification does _not_ specify the features of
> the “HTML document object model”; the _“HTML document object model”
> specification_, whatever that is and applies to a runtime environment, does
> (currently, it would be the HTML 5.1 DOM interfaces, and DOM4, for recent
> versions of Web browsers).

My understanding was based on:

>> | document object model the `window` property of the global object is the
>> | global object itself.

That's why I was using:

(function(global){

}(this));

because this in above will always point to the window object.

https://developer.mozilla.org/en-US/docs/Glossary/Global_object

"In a web browser, any code which the script doesn't specifically start 
up as a background task has a Window as its global object. This is the 
vast majority of JavaScript code on the Web."

> But that aside, if one accepts your premise, then you are using
> 
> |         if (typeof global.self.close === 'function') {
> |             global.self.close();
> |         }
> 
> 1. (AISB,) close() is a *host* object’s method.  You cannot be certain
>     that the result of the `typeof` operation is "function" *everywhere*
>     if that method can be called.  Therefore, some of us have devised
>     isHostMethod() implementations, like jsx.object.isHostMethod().

Fair enough.

> 2. The method has been supported on window objects since
>     the beginning (Netscape Navigator 2.0).  Why feature-test it
>     *in the same window* to begin with?
> 
>     <http://e-pla.net/documents/manuals/javascript-1.0/ref_a-c.html#close_window_method>
> 
> 3. Why not simply
> 
>       window.close();
> 
>     ?

Why not. Some of the methods exists since the beginning.
How do you decide when not to use isHostMethod?

>     Or, if that looks too uncertain, why not

>       (function (global, window) {
>         // … window …
>       }(this, this.window));
> or
> 
>       (function (global) {
>         // … global.window …
>       }(this));
> 
>     ?
Both looks good.

>     The more error-prone `global.self` indirection, at any rate, appears to
>     be unnecessary.
> 
> As for the formatting of the article, I suggest that you do not let code
> lines to be word-wrapped (for me, there are code lines in your article that
> contain only one character from the previous original line).  Not using
> `word-wrap`, and using `overflow-x: auto` instead, enables that; a small
> `padding-right` value should preserve the aesthetics, considering the
> background color.
> 
> Alternatively, you should use `/* … */` for documentation comments (my
> standing code style recommendation; however, in this case, then other code
> lines could still be wrapped in unforeseen ways).

I've removed `word-wrap` and added `overflow-x: auto`. It should looks 
better now.

-- 
Cezary Tomczyk
http://www.ctomczyk.pl/

Thread

why the ! operator can be used to determine a string is null? Xue Feng <xf.lotus@yahoo.com> - 2017-08-08 23:43 +0800
  Re: why the ! operator can be used to determine a string is null? Robert Heller <heller@deepsoft.com> - 2017-08-08 11:16 -0500
  Re: why the ! operator can be used to determine a string is null? Jon Ribbens <jon+usenet@unequivocal.eu> - 2017-08-08 17:40 +0000
    Re: why the ! operator can be used to determine a string is null? Julio Di Egidio <julio@diegidio.name> - 2017-08-08 21:38 -0700
      Re: why the ! operator can be used to determine a string is null? John G Harris <niam@jghnorth.org.uk.invalid> - 2017-08-09 14:51 +0100
    Re: why the ! operator can be used to determine a string is null? Jon Ribbens <jon+usenet@unequivocal.eu> - 2017-08-09 11:01 +0000
      Re: why the ! operator can be used to determine a string is null? "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2017-08-09 16:17 +0200
        Re: why the ! operator can be used to determine a string is null? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-08-09 16:14 +0100
          Re: why the ! operator can be used to determine a string is null? Julio Di Egidio <julio@diegidio.name> - 2017-08-09 10:25 -0700
            Re: why the ! operator can be used to determine a string is null? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-08-09 21:04 +0100
              Re: why the ! operator can be used to determine a string is null? Julio Di Egidio <julio@diegidio.name> - 2017-08-09 13:11 -0700
                Re: why the ! operator can be used to determine a string is null? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-08-10 00:59 +0100
                [ANN] Spam filter for Google Groups (was: why the ! operator can be used to determine a string is null?) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-10 05:06 +0200
                Re: [ANN] Spam filter for Google Groups (was: why the ! operator can be used to determine a string is null?) Julio Di Egidio <julio@diegidio.name> - 2017-08-10 01:00 -0700
                Re: [ANN] Spam filter for Google Groups (was: why the ! operator can be used to determine a string is null?) John G Harris <niam@jghnorth.org.uk.invalid> - 2017-08-10 09:40 +0100
                Re: why the ! operator can be used to determine a string is null? Julio Di Egidio <julio@diegidio.name> - 2017-08-10 00:56 -0700
          Re: why the ! operator can be used to determine a string is null? "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2017-08-09 22:01 +0200
            Re: why the ! operator can be used to determine a string is null? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-08-09 23:35 +0100
              Re: why the ! operator can be used to determine a string is null? "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2017-08-10 10:05 +0200
                Re: why the ! operator can be used to determine a string is null? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-08-10 15:08 +0100
                Re: why the ! operator can be used to determine a string is null? "Evertjan." <exxjxw.hannivoort@inter.nl.net> - 2017-08-10 16:42 +0200
          Re: why the ! operator can be used to determine a string is null? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-09 23:56 +0200
            Re: why the ! operator can be used to determine a string is null? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-08-10 01:40 +0100
              Re: why the ! operator can be used to determine a string is null? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-10 03:44 +0200
                Re: why the ! operator can be used to determine a string is null? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-08-10 03:20 +0100
                Re: why the ! operator can be used to determine a string is null? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-10 04:33 +0200
                Re: why the ! operator can be used to determine a string is null? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2017-08-10 03:57 +0100
  Re: why the ! operator can be used to determine a string is null? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-08 23:20 +0200
    Re: why the ! operator can be used to determine a string is null? Julio Di Egidio <julio@diegidio.name> - 2017-08-08 21:20 -0700
      Re: why the ! operator can be used to determine a string is null? Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-08-09 09:26 +0200
        Re: why the ! operator can be used to determine a string is null? Julio Di Egidio <julio@diegidio.name> - 2017-08-09 01:31 -0700
        Re: why the ! operator can be used to determine a string is null? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-09 11:32 +0200
          Re: why the ! operator can be used to determine a string is null? Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-08-10 09:10 +0200
            Re: why the ! operator can be used to determine a string is null? Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2017-08-10 14:51 +0200
              Re: why the ! operator can be used to determine a string is null? Tim Streater <timstreater@greenbee.net> - 2017-08-10 15:11 +0100
              Re: why the ! operator can be used to determine a string is null? Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2017-08-10 18:52 +0200

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