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Re: Two versions of code - advantages and differences

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Cezary Tomczyk wrote:

[Indentation fixed]

> W dniu 2013-01-04 15:31, Thomas 'PointedEars' Lahn pisze:
>> Cezary Tomczyk wrote:
>>> I have a two versions of code. They are just only examples and contains
>>> simple operations, but I want to understand more deeply some general
>>> things.
>>>
>>> Version 1
>>>
>>> var el = document.getElementById('test');
>>> var fn = function(){
>>>       if( !el ){
>>>           // fallback if el is not available and then return
>>>       }
>>>       return el;
>>> };
>>>
>>> Version 2
>>>
>>> var fn = (function(){
>>>       var el = document.getElementById('test');
>>>
>>>       if(el){
>>>           return function(){
>>>              return el;
>>>           }
>>>       } else {
>>>           // fallback if el is not available and then return
>>>       }
>>> }());
>>
>> […]
>>> […]
>>> Anything else what can be said about advantages or differences between
>>> them?
>>
>> Static code analysis has a hard(er) time recognizing that “fn” actually
>> refers to a function in Version 2.  AFAIK, the JSDoc Toolkit cannot deal
>> with it at all (but my JSdoc is going to).
> 
> True, but they are two different examples.

Your point being?
 
>> Another advantage of Version 1 over Version 2 is that it does not matter
>> if “el” is initialized, or its initialization value is available, before
   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>> or after the definition.  For example, you would not want to use Version
   ^^^^^^^^^^^^^^^^^^^^^^^
>> 2 in a library that is loaded before the document has been loaded,
>> because ”el” will be a false-value then.  The document need not have been
>> parsed to after the element in question, and the document tree not been
>> populated as much, before the document has been loaded.  If you skip the
>> initialization of “el” in Version 1, you can load the code and still
>> initialize “el” later, when appropriate.
> 
> Yes, but the examples are really simple and I wanted to demonstrate some
> general idea. The "el" doesn't have to be always an reference to object.
> This could be anything and could be more complex.

I was pointing out a general problem with self-calling functions, using an 
example.

> I've just wrote something like this:
> 
> var main = {
>      [...]
> 
>      apply : (function(){
>          var tempImg = document.createElement('img'),
>              t, img;
>          tempImg.width = '10';
>          tempImg.height = '10';
> 
>          return function(o){
>              img = tempImg.cloneNode(false);
>              img.alt = o.alt;
>              img.src = o.src;
>              t = document.createElement('span');
>              t.appendChild(document.createTextNode('\u00a0'));
>              t.appendChild(img);
>              t.appendChild(document.createTextNode('\u00a0'));
>              window.setTimeout(function(){ examplefn(t); }, 100);
>          };
>      }
       ^^
JFYI: This is not going to work.
 
>      [...]
> };
> 
> As I understand (correct me if I am wrong) this is inefficient because:
> 
> * closure need extra memory and will be always in memory because
> returned function refers to variables that are outside of returned
> function.
> 
> * "apply" is parsed immediately which is not needed always
> 
> Anything else inefficient or wrong?

Your code does not make sense to me at all, regardless of possible 
inefficiencies.  You are creating on initialization an ”img” object only to 
clone it non-recursively (assuming this works) when the returned function is 
called only to skip the “width” and “height” assignment – seriously?

I would have written

     apply: function (o) {
       var img = document.createElement('img');
       img.width = 10;
       img.height = 10;
       img.alt = o.alt;
       img.src = o.src;

       var t = document.createElement('span');
       t.appendChild(document.createTextNode('\u00a0'));
       t.appendChild(img);
       t.appendChild(document.createTextNode('\u00a0'));
       window.setTimeout(function() { examplefn(t); }, 100);
     }

here, and further optimized (with regard to maintenance effort and 
compatibility) to

     apply: (function () {
       var _createElementFromObj = jsx.dom.createElementFromObj;
       var _runAsync = jsx.dom.timeout.runAsync;

       return function (o) {
         var t = _createElementFromObj({
           type: "span",
           childNodes: [
             "\u00a0",
             {
               type: "img",
               properties: {
                 width: 10,
                 height: 10,
                 alt: o.alt,
                 src: o.src
               }
             },
             "\u00a0"
           ]
         });

         _runAsync(function () { examplefn(t); }, 100);
       };
     }())

(Wrappers like that are functionally optional of course, but I find them 
very useful.  Although it escapes me here why you would want to insert the 
equivalent of “ ” before and after the image; this should be done with 
the “margin” CSS property instead.)

There are times when extra closures are a good idea, and there are times 
when they are not.  There is no definitive answer here, but my code should 
give you some idea.

-- 
PointedEars

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

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Two versions of code - advantages and differences Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2013-01-03 22:58 +0100
  Re: Two versions of code - advantages and differences Stefan Weiss <krewecherl@gmail.com> - 2013-01-04 00:41 +0100
    Re: Two versions of code - advantages and differences Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2013-01-04 09:15 +0100
      Re: Two versions of code - advantages and differences Gregor Kofler <usenet@gregorkofler.com> - 2013-01-04 11:26 +0100
        Re: Two versions of code - advantages and differences Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2013-01-04 14:29 +0100
          Re: Two versions of code - advantages and differences Gregor Kofler <usenet@gregorkofler.com> - 2013-01-04 14:56 +0100
            Re: Two versions of code - advantages and differences Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2013-01-04 16:52 +0100
    Re: Two versions of code - advantages and differences Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2013-01-04 09:19 +0100
  Re: Two versions of code - advantages and differences Gregor Kofler <usenet@gregorkofler.com> - 2013-01-04 11:25 +0100
  Re: Two versions of code - advantages and differences Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-01-04 15:31 +0100
    Re: Two versions of code - advantages and differences David Mark <dmark.cinsoft@gmail.com> - 2013-01-05 08:37 -0800
      Re: Two versions of code - advantages and differences Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-01-05 18:14 +0100
        Re: Two versions of code - advantages and differences David Mark <dmark.cinsoft@gmail.com> - 2013-01-05 10:51 -0800
          Re: Two versions of code - advantages and differences Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-01-05 20:46 +0100
            Re: Two versions of code - advantages and differences David Mark <dmark.cinsoft@gmail.com> - 2013-01-05 17:12 -0800
              Re: Two versions of code - advantages and differences David Mark <dmark.cinsoft@gmail.com> - 2013-01-06 17:43 -0800
              Re: Two versions of code - advantages and differences Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-01-07 03:58 +0100
                Re: Two versions of code - advantages and differences David Mark <dmark.cinsoft@gmail.com> - 2013-01-06 19:23 -0800
                Re: Two versions of code - advantages and differences Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-01-07 05:19 +0100
    Re: Two versions of code - advantages and differences Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2013-01-06 22:30 +0100
      Re: Two versions of code - advantages and differences Stefan Weiss <krewecherl@gmail.com> - 2013-01-07 02:35 +0100
        Re: Two versions of code - advantages and differences Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2013-01-07 22:45 +0100
      Re: Two versions of code - advantages and differences Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-01-07 04:36 +0100
        Re: Two versions of code - advantages and differences Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2013-01-07 23:06 +0100
          Re: Two versions of code - advantages and differences Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2013-01-08 12:35 +0100
            Re: Two versions of code - advantages and differences Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2013-01-09 08:34 +0100
  Re: Two versions of code - advantages and differences David Mark <dmark.cinsoft@gmail.com> - 2013-01-05 09:13 -0800
    Re: Two versions of code - advantages and differences Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2013-01-06 11:09 +0100
      Re: Two versions of code - advantages and differences David Mark <dmark.cinsoft@gmail.com> - 2013-01-06 12:56 -0800
        Re: Two versions of code - advantages and differences Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2013-01-07 22:53 +0100
  Re: Two versions of code - advantages and differences Luc Yen <luc@goal.tw> - 2013-01-05 12:54 -0800
    Re: Two versions of code - advantages and differences Cezary Tomczyk <cezary.tomczyk@gmail.com> - 2013-01-06 21:38 +0100

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