Nodejs重复拒绝（未处理的，在try/catch块中）[重复]

Question

'use strict';

process.on('uncaughtException', (err) => {
  console.error(`uncaughtException: ${JSON.stringify({name: err.name, msg: err.message})}`);
});
process.on('unhandledRejection', (err) => {
  console.error(`unhandledRejection: ${JSON.stringify({name: err.name, msg: err.message})}`);
});

async function create_bug() {
  console.log('In create');
  let res = superCreate();
  console.log(`In create, res = ${res}`);
  let p = new Promise((a, r) => setTimeout(() => a(), 0));
  await p;
  return res;
}


async function superCreate() {
  console.log('superCreate : now throwing');
  throw new Error("Something wrong");
}

async function create_OK() {
  console.log('In create');
  let res = await superCreate();
  console.log(`In create, res = ${res}`);
  let p = new Promise((a, r) => setTimeout(() => a(), 0));
  await p;
  return res;
}

async function main() {
  try {
    let res = await create_bug();
    console.log(`create result : ${res}`);
  } catch (err) {
    console.error(`ERROR caught in main : ${JSON.stringify({name: err.name, msg: err.message})}`);
  }
}

main().then(() => {
  setTimeout(() => console.log(`Finished`), 2000);
});

Answer 1

不等待来自supercreate的变量res中包含的promise，并且在它被拒绝之前也没有附加catch处理程序。因此，触发未处理的promise拒绝。当在main中触发await时，在拒绝之后附加一个处理程序。

请注意，拒绝处理程序会被调用，即使它在promise被拒绝后附加在promise上。尝试例如：

async function main() {
  let res = create_bug();
  try {
    await res;
    console.log(`create result : ${res}`);
  } catch (err) {
    console.error(`ERROR caught in main : ${JSON.stringify({name: err.name, msg: err.message})}`);
  }
  res.catch(err => console.error(`main1: ${JSON.stringify({name: err.name, msg: err.message})}`));
  res.catch(err => console.error(`main2: ${JSON.stringify({name: err.name, msg: err.message})}`));
}

请注意，您现在还将得到“main1”和“main2”错误。

或者，尝试从supercreate函数中删除Async，现在您应该看到create,res=${res}中的没有打印，而是同步处理异常。

还有一种选择是直接从create_bug返回res，而不需要任何await，而是等待main中的res。然后您将看到与原来类似的行为：未处理的拒绝和“正常的”抓取处理块。

async function create_bug() {
  console.log('In create');
  let res = superCreate();
  console.log(`In create, res = ${res}`);
  return res;
}

async function superCreate() {
  console.log('superCreate : now throwing');
  throw new Error("Something wrong");
}

async function main() {
  try {
    let res = create_bug();
    let p = new Promise((a, r) => setTimeout(() => a(), 0));
    await p;
    await res;
    console.log(`create result : ${res}`);
  } catch (err) {
    console.error(`ERROR caught in main : ${JSON.stringify({name: err.name, msg: err.message})}`);
  }
}