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Re: Is this style ok? (bind)

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Stefan Ram wrote:

>   A student in my JavaScript course today showed me his code.
              ^^^^^^^^^^^^^^^^^^^^^^^
OMG.

>   It looked like:
> 
> function v01(){ console.log( "http://example.com/aqeritugh" ); }
> function v02(){ console.log( "http://example.com/eargqqrgh" ); }
> function v03(){ console.log( "http://example.com/grqoqqrug" ); }
> ...
> a.b.c01 = v01;
> a.b.c02 = v02;
> a.b.c03 = v03;
> ...
> 
>   . »console.log« above is just an example. In reality, he called
>   another function, and his functions where a little bit longer.
> 
>   He asked me: »How can I avoid to have to define so many
>   different functions?«
> 
>   My solution was:
> 
> function v(){ console.log( "http://example.com/" + this ); }
> ...
> a.b.c01 = v.bind( "aqeritugh" );
> a.b.c02 = v.bind( "eargqqrgh" );
> a.b.c03 = v.bind( "grqoqqrug" );
> ...
> 
>   Is it good style to use »bind« in this way to implement
>   a kind of function macro?

No.  Function.prototype.bind() was only introduced with ECMAScript Edition 5 
and it creates a new Function instance when is called.  You would end up 
with 4+ Function instances, since the “v” would prevent the original from 
being garbage-collected.

>   When I am thinking about it now, another solution might be:
> 
> function w( text )
> { return function(){ console.log( "http://example.com/" + text ); }}
> ...
> a.b.c01 = w( "aqeritugh" );
> a.b.c02 = w( "eargqqrgh" );
> a.b.c03 = w( "grqoqqrug" );
> ...
> 
>   Is this better or worse?

Better.  More compatible, more efficient, more obvious.

Of course, this begs the question why there would be so many functions in 
the first place, and why they would not use just one function with a 
parameter.

  function y (text)
  {
    console.log("http://example.com/" + text);
  }

And of course, your code style still sucks big time, and I can only hope for 
your students that you do not teach it to them.  In fact, at the moment and 
for some years to come they would be much better off with another teacher, 
one experienced in the field.  But such explains some of the quality of code 
and the misconceptions we have had to be exposed to here and elsewhere…

Bock, Gärtner.
 
>   (I know that
> 
> a.b.c01 = w( "aqeritugh" );
> a.b.c02 = w( "eargqqrgh" );
> a.b.c03 = w( "grqoqqrug" );
> ...
> 
>   still contains redundancy, one could write
> 
> [ "aqeritugh", "eargqqrgh", "grqoqqrug" ].forEach
> ( function( e, i, a ){ a.b[ "c0" + i ]= w( e )); } )

But one should not.  Again, Array.prototype.forEach() is an ES 5 feature, 
and again, efficiency is reduced by n additional function calls and a longer 
effective scope chain.  Instead, write

  for (var a2  = ["aqeritugh", "eargqqrgh", "grqoqqrug"],
           i   = 0,
           len = a2.length;
      i < len; ++i)
  {
    a.b["c0" + a2[i]] = w(e);
  }

or use ”let” if compatibility is not an issue.

-- 
PointedEars
FAQ: <http://PointedEars.de/faq> | SVN: <http://PointedEars.de/wsvn/>
Twitter: @PointedEars2 | ES Matrix: <http://PointedEars.de/es-matrix>
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Re: Is this style ok? (bind) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2014-07-02 05:55 +0200

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