非同期Promiseメソッド

const f1 = (message) => {
  console.log(message);
  return new Promise((res, rej) => {
    setTimeout(() => {
      res('1번 주문');
    }, 3000);
  });
};

const f2 = (message) => {
  console.log('2번', message); // 2번 1번 주문
  return new Promise((res, rej) => {
    setTimeout(() => {
      res('2번 주문');
    }, 1000);
  });
};

const f3 = (message) => {
  console.log('3번', message); //3번 2번 주문
  return new Promise((res, rej) => {
    setTimeout(() => {
      res('3번 주문');
    }, 2000);
  });
};

📌Promise.all

promise

console.time('xx');
Promise.all([f1(), f2(), f3()]).then((res) => {
  console.log(res);
  console.timeEnd('xx'); // 대략 3초
});

function pickAll() {
  return Promise.all([getApple(), getBanana()]).then((fruits) =>
    fruits.join('+')
  );
}

pickAll().then(console.log);

const readAllUsers = () => {

  return new Promise((res, rej) => {
    let one = getDataFromFilePromise(user1Path).then((data) =>
      JSON.parse(data)
    );
    let two = getDataFromFilePromise(user2Path).then((data) =>
      JSON.parse(data)
    );
    Promise.all([one, two]).then((data) => res(data));
  });
};

async

async function order() {
  try {
    const result = await Promise.all([f1(), f2(), f3()]);
    console.log(result);
  } catch (e) {
    console.log(e);
  }
}
console.log('end');

async function order2() {
  let promiseDummy = [Promise 객체, Promise 객체, Promise 객체]

  return Promise.all(promiseDummy)
}

📌Promise.race

console.time('xxx');
Promise.race([f1(), f2(), f3()]).then((res) => {
  console.log(res);
  console.timeEnd('xxx'); // 대략 1초
});

📌Promise.reject

📌Promise.resolve