src/capitalize.js

 /**

  * Capitalizes the first character of a string.

  *

  * @param {string} s - The string to capitalize.

  * @returns {string} - The capitalized string.

  * @throws {TypeError} - If the input is not a string.

  */

 export function capitalize(s) {

  if (typeof s !== 'string') {

  throw new TypeError('Input must be a string');

  }

  if (s.length === 0) {

  return s;

  }

  return s[0].toUpperCase() + s.slice(1);

 }