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Re: Anonymous self-invoking function

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Robert Crandal wrote:

> "Eric Bednarz" wrote:
>> Although the combination of author and group you posted to is unlikely
>> to yield productive answers, you should at least provide the book title
>> and the chapter (ebooks make page numbers problematic).
> 
> It was "Secrets of the JavaScript Ninja", (c) 2013, by John Resig
> and Bear Bibeault.  The code example is in Chapter 2, section 2.4.2,
> page 24.

IIRC that or the previous book by Resig was a one that we discussed here 
already, and that started with stating utter nonsense like "HTML is an 
application of XML" or something similar stupid.  Rest assured that John 
Resig still does not have a clue about what he is doing – as evidenced by 
the inefficient bloated mess that still is jQuery – but he hides it well, 
and many people – especially the uninitiated – fall for appearances (as a 
poor substitute for logic).  Any “secrets” he might be able to reveal to you 
in there would have been discovered by other people, some posting in this 
newsgroup, years before he even started, or are not secrets in any meaning 
of the word at all.

In particular, the so-called Module Pattern (an “anonymous self-invoking 
function”) was popularized, if not invented, by Douglas Crockford, who used 
to post here (before he went down the path of madness that so far and AFAIK 
all JS book authors went).  However, AFAIK even Crockford was not so crazy 
as to suggest you should use “this” in there like that.

>> In any case you should explain exactly what you shortened and/or
>> modified.
>>
>>> /* Anonymous self-invoking function */
>>> (function() {
>>>   this.assert = function assert(a,b) { /* code here */  };
>>>   this.test = function test(a, b) { /* code here */ };
>>> })();
>>>
>>> /* Code for a testing environment or "test groups" */
>>> window.onload = function() {
>>>   test("Test one.", function() {
>>>     assert(true, "Success!");
>>>   });
>>> }
>>>
> 
> The only code that I omitted was the body of the assert()
> and test() functions, and little bit of the code inside the
> window.onload section, which is basically just:
> 
>        window.onload = function() {
>             /* code here that calls test() and assert() */
>        };
> 
> Basically, assert() and test() and defined and made publicly
> accessible in the anonymous self-invoking function as seen
> above.  These functions, test() and assert(), are then called
> during window.onload.  That's the basic gist.

This code, by your own account from a book published/edited in 2013, 
*breaks* in strict mode (with a TypeError in the first line of the function 
body, because “this” is the “undefined” value then), which was introduced 
with ECMAScript Edition 5 in December *2010*, and is recommended for 
production-quality code since then.  QED.

That the functions whose references are assigned to the properties of the 
ECMAScript global object (if not in strict mode) are named is particularly 
unnecessary and error-prone because of the known JScript bug.  Why would an 
“assert” function need a name, why would it need to call itself?  
Compatibility cannot be the reason for the naming because the outer function 
expression already is anonymous.

The proper way is either to explicitly call the function with a reference to 
the global object as the “this” value, or read “this” in global context into 
a variable and use that variable (and to avoid window.onload):

  (function (global) {
    global.assert = function () { … };
  }).call(this);

or

  (function (global) {
    global.assert = function () { … };
  }).call(null);

or

  (function (global) {
    global.assert = function () { … };
  }(this));

Since the latter suffices, and the former two are less compatible, the 
latter should be used.  On the other hand, if the private scope is not 
needed, the proper way is

  function assert ()
  {
    // …
  }

  function test ()
  {
    // …
  }

As for those two functions, however, it is better to have them *not* in the 
global namespace by default so that they do not interfere with the (test 
case) code that is using them.  See also 
<http://PointedEars.de/wsvn/JSX/trunk/test/test.js>.

-- 
PointedEars

Twitter: @PointedEars2
Please do not Cc: me. / Bitte keine Kopien per E-Mail.

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Thread

Anonymous self-invoking function "Robert Crandal" <noreply2me@yahoo.com> - 2013-12-06 18:39 -0700
  Re: Anonymous self-invoking function Eric Bednarz <bednarz@fahr-zur-hoelle.org> - 2013-12-07 03:52 +0100
    Re: Anonymous self-invoking function "Robert Crandal" <noreply2me@yahoo.com> - 2013-12-07 12:31 -0700
      Re: Anonymous self-invoking function Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-12-08 00:17 +0100
        Re: Anonymous self-invoking function Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-12-08 01:08 +0100
          Re: Anonymous self-invoking function Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-12-08 19:41 +0100
          Re: Anonymous self-invoking function jaranmclarn@gmail.com - 2013-12-08 12:21 -0800
        Re: Anonymous self-invoking function "Robert Crandal" <noreply2me@yahoo.com> - 2013-12-09 01:14 -0700
          Re: Anonymous self-invoking function Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-12-10 15:38 +0100
  Re: Anonymous self-invoking function Bjoern Hoehrmann <bjoern@hoehrmann.de> - 2013-12-07 12:28 +0100
    Re: Anonymous self-invoking function Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-12-07 12:57 +0100
  Re: Anonymous self-invoking function Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2013-12-07 16:51 -0200
  Re: Anonymous self-invoking function jaranmclarn@gmail.com - 2013-12-08 12:17 -0800
    Re: Anonymous self-invoking function Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-12-09 00:15 +0100

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