JS Practice — Built-in Objects

String.prototype.toLocaleLowerCase() — numbers and symbols unchanged

📖 Usage Example

'HELLO'.toLocaleLowerCase()   // → 'hello'
'WORLD'.toLocaleLowerCase()   // → 'world'
'ABC123'.toLocaleLowerCase()  // → 'abc123'

Use toLocaleLowerCase() to convert a string to lowercase using the locale-specific rules of the host environment.

String.prototype.toLocaleLowerCase() — Non-Letter Characters

Digits and symbols are not affected by toLocaleLowerCase().

Challenge: Implement lowerLettersOnly(str) that lowercases a string with mixed letters and numbers.

lowerLettersOnly('ABC123') // → 'abc123'

💡 Hints (1)