How to chain a Promise.all with other Promises?

问题

I want to execute my code in the following order:

Promise 1
Wait for 1 to be done, then do Promise 2+3 at the same time
Final function waits for Promise 2+3 to be done

I'm having some trouble figuring it out, my code so far is below.

function getPromise1() {
  return new Promise((resolve, reject) => {
    // do something async
    resolve('myResult');
  });
}

function getPromise2() {
  return new Promise((resolve, reject) => {
    // do something async
    resolve('myResult');
  });
}

function getPromise3() {
  return new Promise((resolve, reject) => {
    // do something async
    resolve('myResult');
  });
}

getPromise1()
.then(
  Promise.all([getPromise2(), getPromise3()])
  .then() // ???
)
.then(() => console.log('Finished!'));

回答1:

Just return Promise.all(...

getPromise1().then(() => {
  return Promise.all([getPromise2(), getPromise3()]);
}).then((args) => console.log(args)); // result from 2 and 3

回答2:

I know it's an old thread, but isn't

() => {return Promise.all([getPromise2(), getPromise3()]);}

a little superfluous? The idea of fat arrow is that you can write it as:

() => Promise.all([getPromise2(), getPromise3()])

which makes the resulting code somewhat clearer:

getPromise1().then(() => Promise.all([getPromise2(), getPromise3()]))
.then((args) => console.log(args)); // result from 2 and 3

Anyway, thanks for the answer, I was stuck with this :)

来源：https://stackoverflow.com/questions/36759061/how-to-chain-a-promise-all-with-other-promises

标签

javascript

es6-promise