JS Practice — Built-in Objects

Array.prototype.findLastIndex() — returns -1 when not found

📖 Usage Example

const arr = [1, 2, 3]
arr.findLastIndex(n => n > 10)  // → -1  (not found)

findLastIndex() returns -1 when no element satisfies the predicate.

Array.prototype.findLastIndex() — no match

Like all index-returning methods, findLastIndex() returns -1 when no element satisfies the predicate.

Challenge: Implement lastNegativeIndex(nums) that returns the index of the last negative number, or -1 if none.

lastNegativeIndex([1, -2, 3, -4]) // → 3
lastNegativeIndex([1, 2, 3])      // → -1

💡 Hints (2)