[LeetCode] Add Two Promises

26 Apr 2024 in Development on Algorithm

• PROBLEMS
  • Description
  • Example
  • Constraints
  • Solution
  • Retrospect

PROBLEMS

Description

---

Given two promises promise1 and promise2, return a new promise. promise1 and promise2 will both resolve with a number. The returned promise should resolve with the sum of the two numbers.

Example

---

Example 1:

Input:
promise1 = new Promise(resolve => setTimeout(() => resolve(2), 20)),
promise2 = new Promise(resolve => setTimeout(() => resolve(5), 60))
Output: 7
Explanation: The two input promises resolve with the values of 2 and 5 respectively. The returned promise should resolve with a value of 2 + 5 = 7. The time the returned promise resolves is not judged for this problem.

Example 2:

Input:
promise1 = new Promise(resolve => setTimeout(() => resolve(10), 50)),
promise2 = new Promise(resolve => setTimeout(() => resolve(-12), 30))
Output: -2
Explanation: The two input promises resolve with the values of 10 and -12 respectively. The returned promise should resolve with a value of 10 + -12 = -2.

Constraints

---

• promise1 and promise2 are promises that resolve with a number

Solution

---

• Runtime: 68ms
• Memory: 49.57MB

/**
 * @param {Promise} promise1
 * @param {Promise} promise2
 * @return {Promise}
 */
const addTwoPromises = async function(promise1, promise2) {
    const firstNum = await promise1
    const secondNum = await promise2
    return firstNum + secondNum
};

/**
 * addTwoPromises(Promise.resolve(2), Promise.resolve(2))
 *   .then(console.log); // 4
 */

Retrospect

---

비동기함수로 이제 들어왔다 많이 써보지는 않았지만 개념은 알고 있는 async await promise에 대한 것들이 나왔다. 처음에 문제를 봤을때 Promise 객체로 받으니까 각 Promise에 대해 await를 걸어줘 Promise를 기다렸다가 숫자를 받아오게끔 처리했다. 그 후 각 받아온 값에 대해 반환을 하여 정답을 구했다.

이번문제는 비동기에 대한 정말 기초적인 개념에 대해서 알려주고 있는거 같다. async를 사용하게 되면 항상 Promise객체를 반환하게 되고 안쪽에서 API를 받아와서 반환하는 로직이 많이 작성되는거 같다.