Type-safe string transforms, complements intrinsic string conversion literal types

type-safe-string-case-transforms.ts

/**
 * Convert first character of string to uppercase
*/
const capitalize = <T extends string>(s: T): Capitalize<T> =>
  `${ s.charAt(0).toUpperCase() }${ s.slice(1) }` as Capitalize<T>;

/**
 * Convert first character of string to lowercase
 */
const uncapitalize = <T extends string>(s: T): Uncapitalize<T> =>
  `${ s.charAt(0).toLowerCase() }${ s.slice(1) }` as Uncapitalize<T>;

/**
 * Convert string to uppercase
 */
const uppercase = <T extends string>(s: T): Uppercase<T> =>
  s.toUpperCase() as Uppercase<T>;

/**
 * Convert string to lowercase
 */
const lowercase = <T extends string>(s: T): Lowercase<T> =>
  s.toLowerCase() as Lowercase<T>;