Redefining a let variable inside a for loop scope doesn't work?

[/#!/JoePea]

> In a little bit of a handwavy example

I imagined a waving hand, holding a piece of chalk with a chalkboard in the
background. Thanks for explaining!

*/#!/*JoePea

On Fri, Jul 15, 2016 at 9:31 AM, J Decker <d3ck0r at gmail.com> wrote:

>
>
> On Fri, Jul 15, 2016 at 7:18 AM, Allen Wirfs-Brock <allen at wirfs-brock.com>
> wrote:
>
>> This is by design.  ECMAScript block scoped declarations generally
>> conform to the principle that within a single block or statement a name may
>> have only a single binding. For example,
>>
>> ```js
>> let x=0;
>> {
>>   let x = x+1;  //access to uninitialized variable error because both the
>> RHS and LHS refer to the inner x
>>                      //which has not yet been initialized when the RHS is
>> evaluated
>> }
>>
>> ```
>>
>> The same principle also applies to
>> ```js
>> let n = {a:[]};
>> for (let n of n.a) ;
>> ```
>>
>> although the actual scoping of the `for` statement is more complex.
>> Basically, such `for` statements consider all names bound by the `let` part
>> of of the `for` header to be undefined while the `of` expression is being
>> evaluated.
>>
>>
> Wouldn't that scope for the 'for' loop declaration allow testing the 'n'
> variable after the loop?  (test to see if it was broken out of completed),
> without requiring extra braces around the for?  (Although sounds like just
> dong
>
> {
>    for( let n ...) {
>    }
>    // can test/use N here?
> }
>
> would also have worked like the workaround for C#/C++?
>
>
>> This is done to avoid any confusion about which `n` the expression
>> references. Such confusion is avoid by all references to the `let` bound
>> names from the RHS errors.
>>
>> Allen
>>
>>
>>
>> _______________________________________________
>> es-discuss mailing list
>> es-discuss at mozilla.org
>> https://mail.mozilla.org/listinfo/es-discuss
>>
>
>
> _______________________________________________
> es-discuss mailing list
> es-discuss at mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.mozilla.org/pipermail/es-discuss/attachments/20160715/98004553/attachment.html>