for-of with `const` variable

# Isiah Meadows (9 years ago)

I was toying around with for-of loops in Node 4.0, and I ran into the following problem:

$ node
> for (let i of [1, 2, 3]) console.log(i)

1
2
3
undefined
> for (const i of [1, 2, 3]) console.log(i)

1
1
1
undefined

That second loop is rather surprising. Is that the correct behavior (in which I need to file an ESLint bug), or is this a V8 bug?

I was toying around with for-of loops in Node 4.0, and I ran into the
following problem:

```
$ node
> for (let i of [1, 2, 3]) console.log(i)
1
2
3
undefined
> for (const i of [1, 2, 3]) console.log(i)
1
1
1
undefined
```

That second loop is rather surprising. Is that the correct behavior
(in which I need to file an ESLint bug), or is this a V8 bug?

-- 
Isiah Meadows

# Jordan Harband (9 years ago)

It's a v8 bug in sloppy mode, in that v8 sloppy mode is still using legacy let/const semantics.

'use strict'; for (const i of [1, 2, 3]) console.log(i) will print out what you expect, since it properly rebinds per iteration.

It's a v8 bug in sloppy mode, in that v8 sloppy mode is still using legacy
let/const semantics.

`'use strict'; for (const i of [1, 2, 3]) console.log(i)` will print out
what you expect, since it properly rebinds per iteration.

On Sat, Oct 17, 2015 at 11:09 PM, Isiah Meadows <isiahmeadows at gmail.com>
wrote:

> I was toying around with for-of loops in Node 4.0, and I ran into the
> following problem:
>
> ```
> $ node
> > for (let i of [1, 2, 3]) console.log(i)
> 1
> 2
> 3
> undefined
> > for (const i of [1, 2, 3]) console.log(i)
> 1
> 1
> 1
> undefined
> ```
>
> That second loop is rather surprising. Is that the correct behavior
> (in which I need to file an ESLint bug), or is this a V8 bug?
>
> --
> Isiah Meadows
> _______________________________________________
> es-discuss mailing list
> es-discuss at mozilla.org
> https://mail.mozilla.org/listinfo/es-discuss
>
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# Isiah Meadows (9 years ago)

Thanks! (I forgot the Node REPL still runs in sloppy mode...)

Thanks! (I forgot the Node REPL still runs in sloppy mode...)

On Sun, Oct 18, 2015 at 2:45 AM, Jordan Harband <ljharb at gmail.com> wrote:
> It's a v8 bug in sloppy mode, in that v8 sloppy mode is still using legacy
> let/const semantics.
>
> `'use strict'; for (const i of [1, 2, 3]) console.log(i)` will print out
> what you expect, since it properly rebinds per iteration.
>
> On Sat, Oct 17, 2015 at 11:09 PM, Isiah Meadows <isiahmeadows at gmail.com>
> wrote:
>>
>> I was toying around with for-of loops in Node 4.0, and I ran into the
>> following problem:
>>
>> ```
>> $ node
>> > for (let i of [1, 2, 3]) console.log(i)
>> 1
>> 2
>> 3
>> undefined
>> > for (const i of [1, 2, 3]) console.log(i)
>> 1
>> 1
>> 1
>> undefined
>> ```
>>
>> That second loop is rather surprising. Is that the correct behavior
>> (in which I need to file an ESLint bug), or is this a V8 bug?
>>
>> --
>> Isiah Meadows
>> _______________________________________________
>> es-discuss mailing list
>> es-discuss at mozilla.org
>> https://mail.mozilla.org/listinfo/es-discuss
>
>



-- 
Isiah Meadows