从Promise对象的实例内执行的setTimeout函数捕获异常 [英] Catching an exception from the setTimeout function executed inside an instance of a Promise object

问题描述

亲爱的参与者，请告诉我解决方法.

Dear participants please tell me the solution.

在此代码块中，catсh方法完美地捕获了异常:

In this block of code, the catсh method perfectly catches the exception:

const myPromise = new Promise(() => {
  throw new Error(`Oops! Threw an exception`);
});

// We catch the exception in the method `catch`.
myPromise
  .catch((error) => console.log(error.message));

在此块中，不会调用catсh方法:

And in this block, the catсh method will not be called:

сonst TIMEOUT = 1000;

const mySecondPromise = new Promise((resolve, reject) => {
  setTimeout(() => {
    throw new Error(`Error in asynchronous function`);
  },
  TIMEOUT
  );
});

mySecondPromise
  .catch(() => console.log(`This code will not be executed`));

请说明:

1. 为什么会发生这种情况(我想这是由于事件循环引起的)?
2. 如何重写代码，以便在catch方法中捕获异常与setTimeout一起工作?

谢谢大家的回答！

这是一个生活例子:

import moment from "moment";

const Delay = (timeout, timePress) => {
    return new Promise((res => setTimeout(() => {
            res(`${moment().format("LTS")} ${timeout} ${timePress}`);
        }, timeout * 1000)
    ));
};

export default Delay;

我想要，如果由于某种原因在setTimeout函数中引发了异常，我应该能够捕获它.像这样:

I want, If for some reason an exception is thrown in the setTimeout function, I should be able to catch it. Like this:

Delay.catch(() => console.log(`This code will not be executed`));

推荐答案

经过一些讨论和评论，我的任务通过这种方法得以解决:

After some discussions and comments, my task was solved by this approach:

const someFunction = timeout => new Promise(resolve => setTimeout(resolve, timeout));

someFunction(timeout).then(() => doSomething()).catch(() => console.log(`This code will not be executed`));

如果异步函数中发生异常:

If an exception occurs in an asynchronous function:

someFunction(timeout).then(ErrorEvent).catch(() => console.log(`This code will not be executed`));

这样的解决方案仍然可行:

Such solutions are still possible:

const testF = () => { throw new Error(`Упс! Бросили исключение.`) }

const genPromise = () => new Promise((resolve, reject) => {
    setTimeout(() => {
        try {
            const res = testF()
            resolve(res)
        } catch (e) { reject(e) }
    }, 1e3)
})

t1: {
    const log = console.log.bind(console, 't1:')
    const _then = log.bind(console, 'then:')
    const _catch = log.bind(console, 'catch:')

    genPromise()
        .then(_then)
        .catch(_catch)
        .then(_then)
}

t2: {
    const log = console.log.bind(console, 't2:')
    const _then = log.bind(console, 'then:')
    const _catch = log.bind(console, 'catch:')

    void async function () {
        let pRes = null
        try {
            pRes = await genPromise()
        } catch (e) {
            _catch(e.message)
        }
        _then(pRes)
    }()
}

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