处理Promise中错误的正确方法 [英] correct way to handle errors inside a Promise

问题描述

当前，我正在尝试确定在Promise中处理错误时应使用的模式.例如，我有下面的代码

Currently, I'm trying to decide what pattern I should use while dealing with errors inside a Promise. For instance, I have the code below

promiseFunc()
.then(result => {

    console.info(`.THEN:: ${result}`)
})
.catch(error => {

    console.info(`.CATCH:: ${error}`)
})

function promiseFunc() {

    return new Promise((resolve, reject) => {

        setTimeout(() => {

            throw Error("setTimeout's callback error")
            resolve('resolution')           
        }, 1000)
    })
}

我无法获得的是，如果其中的一个函数(在我的例子中是setTimeout())抛出错误，则应该使用哪种方法来拒绝Promise.换句话说，我需要一个拒绝而不是一个错误，但是我想到的唯一想法是添加一个try/catch块并从捕获中拒绝Promise.

What I can't get is what approach should be used to reject the Promise if a function inside it (setTimeout(), in my case) throws an Error. In other words, I need a rejection instead of an error, but the only idea that comes to my mind is to add a try/catch block and reject the Promise from the catch.

推荐答案

如果其中的一个函数(在我的例子中是setTimeout())抛出错误，应该使用哪种方法拒绝Promise

What approach should be used to reject the Promise if a function inside it (setTimeout(), in my case) throws an Error

异步回调绝对不能抛出异常.您尝试实现的函数( setTimeout )要么抛出同步异常( new Promise 处理)，要么调用回调.在回调中，您必须调用 resolve 或 reject ，并且必须执行此操作，而不会引发异常.

An asynchronous callback must never throw an exception. Your function that you try to promisify (setTimeout) either throws a synchronous exception (which new Promise handles), or it calls the callback. In the callback you must call resolve or reject, and do so without throwing an exception.

如果您想在回调中做其他事情(除了调用 resolve / reject )，可能会引发异常的事情:不要！

If you want to do additional things in the callback (besides calling resolve/reject), things that could throw an exception: don't!

新的Promise 应该只包装您要承诺的立即函数，而不能包装其他任何东西.在链接到Promise的 then 回调中做更多的事情- then 将在其回调中处理异常:

The new Promise should wrap only the immediate function that you want to promisify, nothing else. Do more things in then callbacks that are chained to the promise - then will handle exceptions in its callback just fine:

function promiseFunc() {
  return new Promise(resolve => {
    setTimeout(resolve, 1000);
//             ^^^^^^^ nothing can go wrong in here
  }).then(() => {
    throw "setTimeout's callback error";
//  ^^^^^ here, it will lead to a rejection
    return "resolution";
  });
}

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