JS Practice — Built-in Objects

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

📖 Usage Example

const arr = [1, 2, 3]
arr.findIndex(n => n > 100)  // → -1  (not found)

findIndex() returns -1 when no element satisfies the predicate — always check for this.

Array.prototype.findIndex() — no match

When no element satisfies the predicate, findIndex() returns -1. This is consistent with indexOf() and lastIndexOf().

Challenge: Implement findGtHundred(nums) that returns the index of the first number greater than 100, or -1 if none.

findGtHundred([10, 200, 50]) // → 1
findGtHundred([1, 2, 3])     // → -1

💡 Hints (2)