JS Practice — Built-in Objects

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

📖 Usage Example

const str = 'hello world'
str.indexOf('world')    // → 6
str.indexOf('xyz')      // → -1
str.indexOf('l')        // → 2

Use indexOf() to find the index of the first occurrence of a substring, returning -1 if not found.

String.prototype.indexOf() — Not Found

Challenge: Implement contains(str, sub) that returns true when sub is found (i.e. indexOf !== -1).

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

💡 Hints (1)