JS Practice — Built-in Objects

String.prototype.indexOf() — empty string always at 0

📖 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() — Empty String

str.indexOf('') always returns 0 regardless of the string content.

Challenge: Implement emptyIndex(str) that returns str.indexOf('').

emptyIndex('hello') // → 0
emptyIndex('')       // → 0

💡 Hints (1)