util.callbackify(original)

• original <Function> 一个 async 函数
• 返回：<Function> 一个回调风格的函数

接收一个 async 函数（或返回 Promise 的函数），并返回一个遵循错误优先回调风格的函数，即将 (err, value) => ... 回调作为最后一个参数。在回调中，第一个参数将是拒绝原因（如果 Promise 成功解决则为 null），第二个参数将是解决的值。

【Takes an async function (or a function that returns a Promise) and returns a function following the error-first callback style, i.e. taking an (err, value) => ... callback as the last argument. In the callback, the first argument will be the rejection reason (or null if the Promise resolved), and the second argument will be the resolved value.】

import { callbackify } from 'node:util';

async function fn() {
  return 'hello world';
}
const callbackFunction = callbackify(fn);

callbackFunction((err, ret) => {
  if (err) throw err;
  console.log(ret);
});const { callbackify } = require('node:util');

async function fn() {
  return 'hello world';
}
const callbackFunction = callbackify(fn);

callbackFunction((err, ret) => {
  if (err) throw err;
  console.log(ret);
});拷贝

将打印：

【Will print:】

hello world 拷贝

回调是异步执行的，并且堆栈跟踪有限。如果回调抛出异常，进程将触发 'uncaughtException' 事件，如果未处理，将退出。

【The callback is executed asynchronously, and will have a limited stack trace. If the callback throws, the process will emit an 'uncaughtException' event, and if not handled will exit.】

由于 null 作为回调的第一个参数具有特殊含义，如果一个封装的函数以假值作为原因拒绝一个 Promise，该值会被封装在一个 Error 中，并且原始值会存储在名为 reason 的字段中。

【Since null has a special meaning as the first argument to a callback, if a wrapped function rejects a Promise with a falsy value as a reason, the value is wrapped in an Error with the original value stored in a field named reason.】

function fn() {
  return Promise.reject(null);
}
const callbackFunction = util.callbackify(fn);

callbackFunction((err, ret) => {
  // When the Promise was rejected with `null` it is wrapped with an Error and
  // the original value is stored in `reason`.
  err && Object.hasOwn(err, 'reason') && err.reason === null;  // true
}); 拷贝