custom-types.js

/** 
 * A User
 * @typedef {Object} User
 * @property {number} id User Id
 * @property {string} name User Name
 * @property {number|string} [age] User Age (optional)
 * @property {boolean} isActive User is active
 */

/**
 * @type {User}
 */
const myNewUser = {
  id: 1,
  name: 'Ryan',
  isActive: true,
  age: 30
};