/**
 * Calculates the sum of two numbers.
 * @param {number} a - The first number
 * @param {number} b - The second number
 * @returns {number} The sum of a and b
 * @example
 * const result = add(2, 3); // 5
 */
function add(a, b) {
  return a + b;
}

/**
 * @typedef {Object} User
 * @property {string} id - Unique identifier
 * @property {string} name - Full name
 * @property {string} email - Email address
 * @property {boolean} [active=true] - Optional, defaults to true
 */

/**
 * Creates a new user.
 * @param {User} userData - The user data
 * @returns {Promise<User>} The created user
 */
async function createUser(userData) {
  // ...
}

/**
 * Represents a user in the system.
 * @class
 */
class User {
  /**
   * Creates a User instance.
   * @param {string} name - User's name
   * @param {string} email - User's email
   */
  constructor(name, email) {
    /** @type {string} */
    this.name = name;
    /** @type {string} */
    this.email = email;
  }

  /**
   * Gets the user's display name.
   * @returns {string} Display name
   */
  getDisplayName() {
    return this.name;
  }
}

/**
 * @callback FetchCallback
 * @param {Error|null} error - Error if failed
 * @param {Object} data - Response data
 */

/**
 * Fetches data from the API.
 * @param {string} url - The URL to fetch
 * @param {FetchCallback} callback - Called with the result
 */
function fetchData(url, callback) {
  // ...
}

/**
 * @template T
 * @param {T[]} array - Array of items
 * @returns {T|undefined} First item or undefined
 */
function first(array) {
  return array[0];
}

/**
 * @module utils/string
 * @description String utility functions
 */

/**
 * Capitalizes the first letter.
 * @param {string} str - Input string
 * @returns {string} Capitalized string
 */
export function capitalize(str) {
  return str.charAt(0).toUpperCase() + str.slice(1);
}