callback-to-promise.js

'use strict';

// Callback Hell example
class UserStorage {
    loginUser(id, password) {
      return new Promise((resolve, reject) => {
        setTimeout(() => {
          if (
            (id === 'sill' && password === 'dream') ||
            (id === 'coder' && password === 'academy')
          ) {
            resolve(id);
          } else {
            reject(new Error('not found'));
          }
        }, 2000);
      });
    }
  
    getRoles(user) {
      return new Promise((resolve, reject) => {
        setTimeout(() => {
          if (user === 'sill') {
            resolve({ name: 'sill', role: 'admin' });
          } else {
            reject(new Error('no access'));
          }
        }, 1000);
      });
    }
}

const userStorage = new UserStorage();
const id = prompt('enter your id');
const password = prompt('enter your password');
userStorage
    .loginUser(id, password)
    .then(userStorage.getRoles)
    .then(user => alert(`Hello ${user.name}, you have a ${user.role} role`))
    .catch(console.log);