Promises vs async / await...

promise-vs-async-await.js

//SET UP

const users = [{
  id: 1,
  name: 'Bob',
  schoolId: 101
}, {
  id: 2,
  name: 'Jane',
  schoolId: 999
}];

const grades = [{
  id: 1,
  schoolId: 101,
  grade: 86
}, {
  id: 2,
  schoolId: 999,
  grade: 100
},{
  id: 3,
  schoolId: 101,
  grade: 80
}];

const getUser = (id) => {
  return new Promise((resolve, reject) => {
    const user = users.find((user) => user.id === id);

    if (user) {
      resolve(user);
    } else {
      reject(`Unable to find user with the id of ${id}.`);
    }
  });
};

const getGrades = (schoolId) => {
  return new Promise((resolve, reject) => {
    resolve(grades.filter((grade) => grade.schoolId === schoolId));
  });
};

//PROMISES....

const getStatus = (userId) => {
  let user;
  return getUser(userId).then ((tempUser) => {
    user = tempUser;
    return getGrades(user.schoolId);
  }).then((grades) => {
    let average = 0;

    if (grades.length > 0) {
      average = grades.map((grade) => grade.grade).reduce((a, b) => a + b) / grades.length;
    }

    return `${user.name} has a ${average}% in the class.`;
  });
};

//ASYNC AWAIT......

const getStatusAlt = async (userId) => {
  const user = await getUser(userId);
  const grades = await getGrades(user.schoolId);
  let average = 0;

  if (grades.length > 0) {
    average = grades.map((grade) => grade.grade).reduce((a, b) => a + b) / grades.length;
  }

  return `${user.name} has a ${average}% in the class.`;
};



getStatusAlt(2).then((status) => {
  console.log(status);
}).catch((e) => {
  console.log(e);
});


getStatus(3).then((status) => {
  console.log(status);
}).catch((e) => {
  console.log(e);
});