事件：'unhandledRejection'

¥Event: 'unhandledRejection'

• reason <Error> | <any> Promise 被拒绝的对象（通常是 Error 对象）。

  ¥reason <Error> | <any> The object with which the promise was rejected (typically an Error object).

• promise <Promise> 被拒绝的 promise。

  ¥promise <Promise> The rejected promise.

每当 Promise 被拒绝并且在事件循环的一个轮询内没有错误句柄附加到 promise 时，则会触发 'unhandledRejection' 事件。使用 Promises 编程时，异常被封装为 "被拒绝的 promise"。拒绝可以使用 promise.catch() 捕获和处理，并通过 Promise 链传播。'unhandledRejection' 事件对于检测和跟踪尚未处理的被拒绝的 promise 很有用。

¥The 'unhandledRejection' event is emitted whenever a Promise is rejected and no error handler is attached to the promise within a turn of the event loop. When programming with Promises, exceptions are encapsulated as "rejected promises". Rejections can be caught and handled using promise.catch() and are propagated through a Promise chain. The 'unhandledRejection' event is useful for detecting and keeping track of promises that were rejected whose rejections have not yet been handled.

import process from 'node:process';

process.on('unhandledRejection', (reason, promise) => {
  console.log('Unhandled Rejection at:', promise, 'reason:', reason);
  // Application specific logging, throwing an error, or other logic here
});

somePromise.then((res) => {
  return reportToUser(JSON.pasre(res)); // Note the typo (`pasre`)
}); // No `.catch()` or `.then()`const process = require('node:process');

process.on('unhandledRejection', (reason, promise) => {
  console.log('Unhandled Rejection at:', promise, 'reason:', reason);
  // Application specific logging, throwing an error, or other logic here
});

somePromise.then((res) => {
  return reportToUser(JSON.pasre(res)); // Note the typo (`pasre`)
}); // No `.catch()` or `.then()`拷贝

以下也将触发 'unhandledRejection' 事件被触发：

¥The following will also trigger the 'unhandledRejection' event to be emitted:

import process from 'node:process';

function SomeResource() {
  // Initially set the loaded status to a rejected promise
  this.loaded = Promise.reject(new Error('Resource not yet loaded!'));
}

const resource = new SomeResource();
// no .catch or .then on resource.loaded for at least a turnconst process = require('node:process');

function SomeResource() {
  // Initially set the loaded status to a rejected promise
  this.loaded = Promise.reject(new Error('Resource not yet loaded!'));
}

const resource = new SomeResource();
// no .catch or .then on resource.loaded for at least a turn拷贝

在此示例情况下，可以将拒绝作为开发者错误进行跟踪，这通常是其他 'unhandledRejection' 事件的情况。为了解决此类故障，可以将非操作 .catch(() => { }) 句柄附加到 resource.loaded，这将阻止触发 'unhandledRejection' 事件。

¥In this example case, it is possible to track the rejection as a developer error as would typically be the case for other 'unhandledRejection' events. To address such failures, a non-operational .catch(() => { }) handler may be attached to resource.loaded, which would prevent the 'unhandledRejection' event from being emitted.

如果 'unhandledRejection' 事件已触发但未被处理，它将被抛出为未捕获的异常。这以及 'unhandledRejection' 事件的其他行为可以通过 --unhandled-rejections 标志进行更改。

¥If an 'unhandledRejection' event is emitted but not handled it will be raised as an uncaught exception. This alongside other behaviors of 'unhandledRejection' events can changed via the --unhandled-rejections flag.