I don't get it. Please give an example of the per-iteration initialization in the while loop... (the for-loop version before `;` does it before iteration, not per-iteration)
On Mon, 26 Mar 2018 at 07:20 Isiah Meadows <[email protected]> wrote: > As a counterpoint, Rust and Swift are the opposite: it's only defined > in the consequent branch, not the alternate. So it could go both ways. > > But if a value is useful in both branches, I'd prefer to just define > the variable in a separate statement, to clarify that it's useful in > both branches (explicit > implicit). To take your example, I'd prefer > instead to do this: > > ```js > let foo = getFoo() > > if (foo.isReady()) { > foo.start() > } else { > foo.wait() > } > ``` > ----- > > Isiah Meadows > [email protected] > > Looking for web consulting? Or a new website? > Send me an email and we can get started. > www.isiahmeadows.com > > > On Sun, Mar 25, 2018 at 5:42 AM, Maël Nison <[email protected]> wrote: > > C++ defines it as being available in both branches, I think we try to > share > > the same behavior. Keep in mind that it will useful when the check is on > > something different than existence : > > > > if (let foo = getFoo() ; foo.isReady()) > > foo.start(); > > else > > foo.wait(); > > > > On Wed, Mar 21, 2018, 10:27 PM Isiah Meadows <[email protected]> > wrote: > >> > >> My implication was that it'd only be available in the `if` (if > >> declared with `let`/`const`). > >> ----- > >> > >> Isiah Meadows > >> [email protected] > >> > >> Looking for web consulting? Or a new website? > >> Send me an email and we can get started. > >> www.isiahmeadows.com > >> > >> > >> On Wed, Mar 21, 2018 at 6:25 PM, Sebastian Malton < > [email protected]> > >> wrote: > >> > Sorry if I missed a message but would such an initialization be only > >> > available in the first `if` block or also in the subsequent `else if` > and > >> > `else` blocks? > >> > > >> > Sebastian Malton > >> > > >> > > >> > Original Message > >> > From: [email protected] > >> > Sent: March 21, 2018 6:18 PM > >> > To: [email protected] > >> > Cc: [email protected]; [email protected] > >> > Subject: Re: Proposal: if variable initialization > >> > > >> > 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 > >> > [email protected] > >> > > >> > Looking for web consulting? Or a new website? > >> > Send me an email and we can get started. > >> > www.isiahmeadows.com > >> > > >> > > >> > 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. > >> >> > >> >> > >> >> _______________________________________________ > >> >> 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 > _______________________________________________ > es-discuss mailing list > [email protected] > https://mail.mozilla.org/listinfo/es-discuss >
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