I am not sure I am missing something but I think arguments could disappear
without problems, being easily simulated like this:
function f1(...arguments) {
f2.apply(this, arguments);
f2(...arguments);
let [a,b,c,...rest] = arguments;
// etc etc
}
Am I wrong ?
br
On Wed, Oct 26, 2011 at 6:07 PM, Xavier MONTILLET
<[email protected]>wrote:
> http://wiki.ecmascript.org/doku.php?id=harmony:rest_parameters
>
> Hi,
>
> Here is the behavior I would like:
>
> function f( a, b, ...rest ) { }
> f( 1, 1 );// ok
> f( 1, 1, 1 );// ok
> f( 1, undefined );// ok
> f( 1 );// Error: missing parameter
>
> Because since you can't reference a and b as properties of an object
> anymore, there is no way you can know whether they are undefined
> because the value given was undefined or because no value was given.
>
> Of course, no such error would happen if there is a default value:
>
> function f( a, b=1, ...rest ) { }
>
> ---------------------------------------------------
>
> If you consider throwing an error a bit too harsh, you should consider
> giving arguments.length. Not withing arguments but as a separate
> variable.
>
> function f( a, b, ...rest ) {
> var awesomeNameYoullFind = f.length + rest.length; // this should
> be provided by core
> if ( awesomeNameYoullFind < 2 ) {// and people who want to throw
> errors will have a convenient way of doing it
> throw Error();
> }
> }
>
> -----------------------------------------------------
>
> Another thing I think arguments shouldn't disappear. It sucks that it
> isn't an array but it still has some use-cases.
>
> e.g. a function that delegates in certain conditions
>
> function f( a, b, ...rest ) {
> if ( a ) {
> f2.apply( this, arguments );
> // or f2( ...arguments );
> } else {
> // w/e
> }
> }
>
> This could be done that way:
>
> function f( a, b, ...rest ) {
> if ( a ) {
> f2( a, b, ...rest );
> } else {
> // w/e
> }
> }
>
> But what if you have a, b, c, d and so on? You don't want to copy all
> those variable names.
> And what if you want to delegate everything except a and b? Without an
> argu,ments object, it's bothersome. With it, you just slice from index
> 2...
>
> To give a real example: assertions.
>
> I use to do things like that:
>
> function f( a, b, c, d ) {
> assertArguments( arguments, [
> {// a
> type: 'number'
> },
> {// b and c
> type: 'string',
> length: 2
> },
> {// d
> type: 'object',
> optionnal: true
> }
> ] );
> }
>
> And if you remove the arguments object, it gets really bothersome...
> You have to make sure you pass every single arguments in the good
> order...
>
> ------------------------------------------------------------
>
> But of course, it should become a real array (and probably change its
> name to args or something similar). And to prevent from breaking
> existing codes, if there is already a variable named args in the scope
> or a parent scope *and it is not the args created for another
> function*, replace it.
>
> var args = 1;
> function f( ) {
> // here args is 1 no matter what
> }
> f(0);
>
> function f1( ) {
> // here args is the arguments from f1
> function f2( ) {
> // here args is the arguments from *f2*
> // because even though it was in the scope, some magic
> happened and the engine figured out it wasn't a variable declared by
> the user
> }
> f2(2);
> }
> f1(1);
>
> --------------------------------------------------------
>
> PS: If a new arguments object is created, then there is no use for
> awesomeNameYoullFind.
> _______________________________________________
> 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
