Thanks for the feedback, allow me to explain the rationale for Array.of:
One of the main goals of ES6 is to become a better language for library writers
and code generators.
For compilation targets, ES/JS can't assume that implementations will always
know what its factories are expected to construct:
Imagine the following piece of code is used in a VM (think Dart->JS, LLJS->JS)
var o = (function( construct, ...rest ) {
return new construct( rest );
})( factory [, variable arity args] );
If factory is Array and only one numeric arg is given, inline like this:
var o = (function( construct, ...rest ) {
return new construct( rest );
})( Array, 10 );
The result of `o` will be an array with 10 empty indexes, as if it were called
like:
new Array(10)
If you replace that by using Array.of(), you avoid this "gotcha"
More comments inline...
On Sunday, August 26, 2012 at 5:53 AM, Shijun He wrote:
> Hi,
>
> I don't think Array.of() is useful, just stick on array literal seems enough:
>
> var a = [1,2,3]
> var a1 = [3]
>
> Why we need this:
>
> var a = Array.of(1,2,3)
> var a1 = Array.of(3)
>
> Is there any special benefit I missed?
>
Explained above :)
>
>
> And there is another reason why I don't like Array.of() , myself write
> a small library which use Array.of(type) to get a "strong-typed"
> array:
>
> var StringArray = Array.of(String)
> var a = StringArray.from(['a', 1, true]) // ['a', '1', 'true']
> a.push('string') // ['a', '1', 'true', 'string']
> a.push(100) // throws error
>
> And Function.of() :
>
> var sqrt = Function.of(Number).from(Math.sqrt)
> sqrt(9) // 3
> sqrt('9') // error
> sqrt(9, 'unwanted') // error
>
>
I'd argue that if code is extending ES built-ins with non-standard properties,
it accepts the risk that one day it may be in conflict.
Rick
>
>
> --
> hax
> _______________________________________________
> es-discuss mailing list
> [email protected]
> https://mail.mozilla.org/listinfo/es-discuss
>
>
_______________________________________________
es-discuss mailing list
[email protected]
https://mail.mozilla.org/listinfo/es-discuss
