JS Practice — Built-in Objects

String.prototype.charCodeAt() — detect lowercase

📖 Usage Example

const str = 'ABC'
str.charCodeAt(0)   // → 65
str.charCodeAt(1)   // → 66
str.charCodeAt(99)  // → NaN

Use charCodeAt() to get the UTF-16 code unit value of the character at the given index.

String.prototype.charCodeAt() — Lowercase Detection

Lowercase letters have codes 97–122. You can use this to detect if a character is lowercase.

Challenge: Implement isLowercase(ch) that returns true if the single character is lowercase using .charCodeAt(0).

isLowercase('a') // → true
isLowercase('A') // → false

💡 Hints (1)