I have this repro: https://codesandbox.io/s/jolly-bogdan-k6ii4?file=/src/index.ts

code:

const wait = (timeoutMs: number) => {
  let timeoutHandle: number | undefined;

  const promise = new Promise((_resolve, reject) => {
    timeoutHandle = setTimeout(() => {
      reject(`wait timed out after ${timeoutMs} ms`);
    }, timeoutMs);
  });

  return {
    promise,
    cancel: (): void => clearTimeout(timeoutHandle)
  };
};

const waitBy = (timeoutMs: number) => {
  const res = wait(timeoutMs);
  return res;
};

const main = async () => {
  try {
    const { promise, cancel } = waitBy(3000);
  } catch (error) {
    console.log("failed on timeout");
  }
  // try {
  //   await promise;
  // } catch (error) {
  //   console.log("timed out");
  // }
};

main();

When this is ran in Node.js, the reject will throw after 3s, and blow up the whole process with an "unhandledRejection Error" - where can one catch this error to avoid an unhandledRejection Error, but allow it to propagate up to the catch inside the main function?

CodePudding user response：

You need to await it.

const main = async () => {
  try {
    const { promise, cancel } = waitBy(3000);
    const res = await promise;
  } catch (error) {
    console.log("failed on timeout");
  }
};

CodePudding user response：

The problem is that you're not waiting for the promise to resolve before moving forward and the error is thrown then outside of the try block.

const main = async () => {
  try {
    const { promise, cancel } = waitBy(3000);
    await promise // new code
  } catch (error) {
    console.log("failed on timeout");
  }
  // try {
  //   await promise;
  // } catch (error) {
  //   console.log("timed out");
  // }
};