sorry you get 1, and need again to subtract the array length, `arr.length -1 - 1` to get the final result 3
Le mer. 18 juil. 2018 à 18:41, Cyril Auburtin <[email protected]> a écrit : > there you go > ``` > console.log([7, 4, 6, 7, 12].findIndex((_, i, a) => > isPrime(a[a.length-1-i]))); // 3 > ``` > > Le mer. 18 juil. 2018 à 11:17, Dmitry Shulgin <[email protected]> a > écrit : > >> >> ---------- Forwarded message ---------- >> From: Dmitry Shulgin <[email protected]> >> Date: 2018-07-05 10:36 GMT+03:00 >> Subject: Feature proposal >> To: [email protected] >> >> >> I came across a task of finding an index of the last element in array >> that satisfies the condition, so i reversed array and found it by *findIndex >> *function. >> I was thinking: >> Why do we have *findIndex*` method, but no *findLastIndex*? >> It seems logical to follow *[index|lastIndex]Of* pair, doesn't it? >> Reversing array in this case seems too complicated to me. >> >> So, i would like to suggest new method like >> *Array.prototype.findLastIndex()* >> >> Example: >> >> function isPrime(element, index, array) { >> var start = 2; >> while (start <= Math.sqrt(element)) { >> if (element % start++ < 1) { >> return false; >> } >> } >> return element > 1; >> } >> >> console.log([4, 6, 8, 12].findIndex(isPrime)); // -1, not found >> console.log([7, 4, 6, 7, 12].findIndexLast(isPrime)); // 3 >> >> >> Would be glad to implement, if it makes sense. >> >> Thx for replies. >> >> P.S. Small issue on GitHub was closed due to offtop (not an issue, as i >> understand). >> https://github.com/tc39/ecma262/issues/1253 >> >> _______________________________________________ >> es-discuss mailing list >> [email protected] >> https://mail.mozilla.org/listinfo/es-discuss >> >
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