JS Practice — Built-in Objects

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

📖 Usage Example

const arr = [1, 2, 3]
arr.lastIndexOf(9)  // → -1  (not found)

lastIndexOf() returns -1 when the value is not present anywhere in the array.

Array.prototype.lastIndexOf() — not found

When the search value is not present in the array, lastIndexOf returns -1. This mirrors the behavior of indexOf.

Challenge: Implement notFound(arr, val) that returns the result of arr.lastIndexOf(val) (which will be -1 when the value is absent).

notFound([1, 2, 3], 99) // → -1
notFound([], 0)         // → -1

💡 Hints (2)