8ee50178f3
Correct: `Array.from()` (it’s a static method) Incorrect: `Array.join()` (doesn’t exist; it’s a prototype method) This patch uses the common `#` syntax to denote `.prototype.`.
560 B
560 B
findLastIndex
Returns the index of the last element for which the provided function returns a truthy value.
Use Array.prototype.map() to map each element to an array with its index and value.
Use Array.prototype.filter() to remove elements for which fn returns falsey values, Array.prototype.pop() to get the last one.
const findLastIndex = (arr, fn) =>
arr
.map((val, i) => [i, val])
.filter(([i, val]) => fn(val, i, arr))
.pop()[0];
findLastIndex([1, 2, 3, 4], n => n % 2 === 1); // 2 (index of the value 3)