JS Practice — Built-in Objects

String.prototype.toUpperCase() — already uppercase unchanged

📖 Usage Example

'hello world'.toUpperCase()   // → 'HELLO WORLD'
'abc'.toUpperCase()           // → 'ABC'
'xyz123'.toUpperCase()        // → 'XYZ123'

Use toUpperCase() to convert all alphabetical characters in a string to uppercase.

String.prototype.toUpperCase() — Already Uppercase

If all letters are already uppercase, toUpperCase() returns an equivalent string.

Challenge: Implement ensureUppercase(str) using toUpperCase.

ensureUppercase('HELLO') // → 'HELLO'

💡 Hints (1)