Add Two Promises – 2723

🔗LC2723 🟢 Easy 🧩 Pattern – Promises and Time

📅 Day 12/30 Days of JavaScript

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

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.

Solution

/**
 * @param {Promise} promise1
 * @param {Promise} promise2
 * @return {Promise}
 */
var addTwoPromises = async function (promise1, promise2) {
    const result1 = await promise1;
    const result2 = await promise2;
    return result1 + result2;
};

// Using Promise.all([array of promises to await])
var addTwoPromises = async function (promise1, promise2) {
    const [result1, result2] = await Promise.all([promise1, promise2]);
    return result1 + result2;
};

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