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Re: Two versions of code - advantages and differences

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W dniu 2013-01-07 04:36, Thomas 'PointedEars' Lahn pisze:
> Cezary Tomczyk wrote:
[...]
>>> Cezary Tomczyk wrote:
[...]
>>>> 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
>>>>        }
>>>> }());
[...]

>>> 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?

I was thinking that even if the functions are different then variable 
name is the same. I thought that JSdoc will catch this, but this doesn't 
make sense. When both of functions will be used in the same scope then 
Version 2 will overwrite Version 1.

[...]
>> 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.

Indeed.

>> 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.

Sorry, fast typing. A typo.

>>       [...]
>> };
>>
>> 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 made a test and seems that creating once img node with properties and 
clone them later every time is faster than creating new img node and 
adding new properties. Just a small optimization.

> 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);
>       }

Yes. After some discuss in this topic I would change it to a simpler 
version.

> 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.)

Tried to use CSS, but it doesn't work for img. See:
http://jsfiddle.net/w7BAu/

Tested on Firefox 17.0.1 and IE9 (Windows 7, 64 bit).

> 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.

I think that I created little bit overcomplicated my code and now I 
rewrite it in a simpler version. No need extra closure in that case, 
like mine.

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

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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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