My proposed semantics does similar, except I just read until it matches, then I skip it and incrementally copy the rest in a separate loop (avoiding an extra branch). I `delete` the remaining parts in the polyfill, but you wouldn't need to do that with normal arrays (just non-array array-likes).
As for performance, branch prediction matters a lot more than local variable assignment, and sequential array iteration usually hits the CPU cache line in any JIT. ----- 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 Fri, Nov 10, 2017 at 7:24 AM, Bob Myers <[email protected]> wrote: > Thanks for your optimization. In one of my library routines I further > optimize this with > > ```js > if (elt === item) { > changed = true; > } else { > if (changed) { array[j] = elt; } > j++; > } > ``` > > To avoid unnecessary assignments (which might be expensive--I don't know, > are they?) while you're still in the portion of the array before the first > element to be removed. > > On Fri, Nov 10, 2017 at 5:39 PM, T.J. Crowder > <[email protected]> wrote: >> >> On Fri, Nov 10, 2017 at 11:41 AM, Bob Myers <[email protected]> wrote: >> > >> > What's wrong with this? >> >> I had the impression he was trying to avoid callbacks, just using `===`. >> But other than a missing `const` on the `for-of`, it looks nice and >> efficient -- except that [it doesn't seem like `for-of` on arrays with the >> default iterator is much optimized yet][1]. FWIW: >> >> ```js >> function removeFromArray(array, item) { >> let changed = false; >> let j, i, len, elt; >> >> for (j = i = 0, len = array.length; i < len; ++i) { >> elt = array[i]; >> if (elt === item) { >> changed = true; >> } else { >> array[j++] = elt; >> } >> } >> >> array.length = j; >> return changed; >> } >> ``` >> >> Clunkier but apparently we're optimizing for speed... >> >> -- T.J. Crowder >> >> [1]: https://jsperf.com/for-of-vs-for-with-const-binding/1 > > _______________________________________________ es-discuss mailing list [email protected] https://mail.mozilla.org/listinfo/es-discuss
