node.js - 等到所有 promise 完成

Question

我如何知道 for 循环内的所有 Promise 何时完成执行？有更好的方法吗？

for (let index = 0; index < array.length; index++) {
  request(array[index], function (error, response, body) {
    promise1().then(result1 => {
      if (result1 !== 0) {
        promise2().then(result2 => {
          promise3(result2);
        }
      } else {
        promise3(result1);
      }
    });
  });
}

console.log('all promises finished');

Answer 1

通过将代码转换为使用 async/await 将项目映射到 Promise，然后使用标准 Promise.all() 等待所有 promise 解决的函数:

// promisified request()
const requestP = item =>
  new Promise((resolve, reject) => {
    request(item, (error, response, body) => {
      if (error) return reject(error);
      resolve({ response, body });
    });
  });

const processItem = async item => {
  const { response, body } = await requestP(item);
  const result1 = await promise1(/* this probably uses response or body? */);
  if (result1 !== 0) {
    const result2 = await promise2();
    return await promise3(result2);
  } else {
    return await promise3(result1);
  }
};

const promises = array.map(processItem);

Promise.all(promises).then(() => {
  console.log("all promises finished");
});