I'm personally very much *for* this `if (var ...; cond) { ... }`
syntax. I couldn't tell you how many times I would've liked something
to that effect, since that's probably one of my biggest areas of
boilerplate.
I would also be in favor of `if (var ...) { ... }` as a shorthand that
guards `!= null` the expression result (pre-match), since that's about
90% of my use cases for it. There *is* a potential area of ambiguity
in sloppy for `if ( let [ x ] = y )`, since that would be currently
parsed as `var tmp = y; let[x] = tmp; if (tmp) { ... }`, but I doubt
breaking that would be of much web compat risk. (A similar ambiguity
existed with `for (let [`, but that break didn't cause many issues.)
-----
Isiah Meadows
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On Wed, Mar 21, 2018 at 2:47 PM, Mike Samuel <[email protected]> wrote:
>
>
> On Wed, Mar 21, 2018 at 1:27 PM, Sebastian Malton <[email protected]>
> wrote:
>>
>> Because block-level scoping is a very good way to avoid certain bugs and
>> is easier to reason about. Especially when considering project successors.
>
>
> +1. function-scoped variables in loop bodies caused tons of bugs before
> let-scoped variables and were a main motivating case.
>
> var i;
> for (i = 0; i < arr.length; ++i) {
> f(function () { /* Do something with */ arr[i]; });
> }
>
> vs
>
> for (let i = 0; i < arr.length; ++i) {
> f(function () { /* Do something with */ arr[i]; });
> }
>
> Yes, linters got pretty good at finding uses of closed-over variables
> modified in a loop, but the workarounds were not ideal.
>
> var i;
> for (i = 0; i < arr.length; ++i) {
> f(function (i) { return function () { /* Do something with */ arr[i]; }
> }(i));
> }
>
> Block scoping is just better for code that uses loops, variables, and
> function expressions.
>
>
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>
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