如何在异步 function 中使用 while 循环 - 新手问题

Question

Why isn't this function to loop through an array returning to where I called it? I'm pretty sure it's something to do with my use of while inside an async function, but I can't figure it out.

I tried to use return after the while loop, but that fires straight away because of the async, and I couldn't work out how to put it inside the loop successfully either.

All help appreciated.

This is a simplification of the code:

let cardsData

async function assignDatesToAllCards() {
  await doAThing()
  let n = cardsData.length
  let i = 0
  await loopToSetDates()
  console.log("data ready") // this doesn't execute

  async function loopToSetDates() {
    while (i <= n) {
        let sendDate = await calculateSendDate(aDate)
        cardsData[i].sendDate = sendDate
        i++;
    }
  }
}

And this is the full code:

let cardsData

async function assignDatesToAllCards() {
  console.log("assigning dates...");
  await setCardsDataArray() //refreshes cardsData
  let n = cardsData.length
  console.log("n:" + n)
  let i = 0
  await loopToSetDates()
  console.log("Cards about to Update"); // this doesn't execute
  wixData.bulkUpdate("UserCard", cardsData) //nor does this

  async function loopToSetDates() {
    while (i <= n) {
        console.log("i:" + i);
        let targetDeliveryDate = await calculateTargetDeliveryDate(firstDate, i * frequency)
        let sendDate = await calculateSendDate(targetDeliveryDate)
        cardsData[i].targetDeliveryDate = targetDeliveryDate
        cardsData[i].sendDate = sendDate
        console.log(cardsData[i]);
        i++;
    }
  }
}

Answer 1

I'm not sure if your other functions resolve the promises. But you can try something like the below one. I will be adding dummy promises.

async function assignDatesToAllCards() {
  console.log("assigning dates...");
  let n = 2;
  console.log("n:" + n)
  let i = 0
  await loopToSetDates()
  console.log("Cards about to Update"); // this doesn't execute
  console.log("UserCard") //nor does this

  async function loopToSetDates() {
    while (i <= n) {
        console.log("i:" + i);
        let x = await prompt();
        console.log(x);
        i++;
    }
    return true;
  }
}

assignDatesToAllCards();```

This is working.
Hope this helps

Answer 2

replace

while (i <= n)

with

while (i < n)

I was trying to loop one too many times.

On reflection I should have wrapped the awaits in a try...catch... and I would have found the error much more quickly.

Thanks for all your contributions