Does it mutate 😱

Array.prototype.findLastIndex

No mutation

Description

The findLastIndex() method of Array instances iterates the array in reverse order and returns the index of the first element that satisfies the provided testing function. If no elements satisfy the testing function, -1 is returned.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/findLastIndex

Example

const array1 = [5, 12, 50, 130, 44];

const isLargeNumber = (element) => element > 45;

console.log(array1.findLastIndex(isLargeNumber));
// Expected output: 3
// Index of element with value: 130