Type Alias UpperAlphabet

UpperAlphabet: Uppercase<LowerAlphabet>

Represents the set of uppercase English alphabet letters. A union of string literals from 'A' to 'Z'. Derived by applying the built-in Uppercase utility type to LowerAlphabet.

Example

type FirstLetter<S extends string> = S extends `${infer F}${string}`
  ? F extends UpperAlphabet
    ? F
    : never
  : never;

type T1 = FirstLetter<'Hello'>; // 'H'
type T2 = FirstLetter<'world'>; // never

const isUppercase = (char: string): char is UpperAlphabet => {
  return char.length === 1 && char >= 'A' && char <= 'Z';
};

Type Alias UpperAlphabet

Example

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