为什么这个等待返回未定义？

Question

I have the following code:

const checkBatchStatus = async (batchId: number) => {
let result = await fetchcall("POST", "api/batch/status", { "BatchId": batchId })
    .then(result => {     
        Promise.resolve(true);
    })
    .catch(err => {
        Promise.resolve(false);
    });
};

the caller code is the following:

async function isBatchRequestCompleted(batchId: number) {

    let status = await checkBatchStatus(batchId);
    console.log(`status is ${status}`);

status is always undefined. Not understanding why.

If I change the checkBatchStatus to simply return false, then I get status equal to false.

const checkBatchStatus = async (batchId: number) => {
    return false;
};

Can a kind soul explain to me what I am seeing?

Answer 1

You didn't return a value in the function checkBatchStatus() . And calling a Promise.resolve() in callback function of .then() is a wrong idea if you want just a Boolean value.

const checkBatchStatus = (batchId: number) => {
  return fetchcall("POST", "api/batch/status", { "BatchId": batchId })
    .then(result => {     
        return true;
    })
    .catch(err => {
        return  false;
    });
};

Answer 2

You're mixing both promises and async/await unnecessarily here. I suggest sticking with one or the other.

async / await :

const checkBatchStatus = async (batchId: number) => {
  try {
    await fetchcall("POST", "api/batch/status", { "BatchId": batchId });
    return true;
  } catch {
    return false;
  }
};

Or promises:

const checkBatchStatus = (batchId: number) => {
  return fetchcall("POST", "api/batch/status", { "BatchId": batchId })
    .then(result => true)
    .catch(err => false);
};