JS Practice — Built-in Objects

String.prototype.lastIndexOf() — not found returns -1

📖 Usage Example

const str = 'abcabc'
str.lastIndexOf('a')    // → 3
str.lastIndexOf('z')    // → -1
str.lastIndexOf('b', 3) // → 1

Use lastIndexOf() to find the index of the last occurrence of a substring, searching from right to left.

String.prototype.lastIndexOf() — Not Found

Challenge: Implement notPresent(str, sub) that returns true when sub is not in str.

notPresent('hello', 'xyz') // → true
notPresent('hello', 'ell') // → false

💡 Hints (1)