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Re: Style: new String( "abc" )

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Stefan Ram wrote:

>   IIRC, I read somewhere that one should prefer to use
>   primitives such as "abc"; one should not create objects
>   via »new String ( "abc )« (or, »new Number( 7 )«).
> 
>   I am not sure why »new String( "abc" )« should be bad style.

Certainly there is nothing wrong per se in having objects that are 
“instanceof String”, see e.g. 
<http://PointedEars.de/wsvn/JSX/string/unicode.js>.

But consider, for example, what

  var b = new Boolean(false);
  var b = new Number(0);
  var s = new String("");

would do in

  if (b && n && s)

when used instead of

  var b = false;
  var n = 0;
  var s = "";

>   For example, I consider the following piece of code:
> 
> { "abc".charAt( 0 );
>   "abc".charAt( 1 );
>   "abc".charAt( 2 ); }
> 
>   (Of course, the example with »"abc".charAt( 0 );« is nonsense.)

Why is it nonsense?

>   . Above, AFAIK, the primitve "abc" was implicitly converted
>   into an object /three times/.

Not necessarily as *these* expressions can be optimized by a compiler to

  "a"
  "b"
  "c"

respectively.

>   If one would have written:
> 
> { let abc = new String( "abc" );
>   abc.charAt( 0 );
>   abc.charAt( 1 );
>   abc.charAt( 2 ); }
> 
>   only one object would have been created.

Not necessarily.  In fact, that you are declaring the variable in block 
scope using “let” makes it possible to optimize here easily as there is no 
code outside of the block that could change the value of *that* “abc”.  
Assuming, of course, that “String” still has its initial value.

-- 
PointedEars
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Re: Style: new String( "abc" ) Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-06-02 22:39 +0200

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