node.js - Global exception handling in Express

Question

1. Is the following server configuration to capture routing exceptions correct?
server.js

const express = require("express");
const app = express();

// ...加载中间件


// ...配置路由

// 异常处理
// 如果是开发环境，则打印异常到控制台
if (app.get("env") === "development") {
  app.use((err, req, res, next) => {
    console.error("Error",err);
    next(err);
  });
}

// 如果是非开发环境，则向页面输出错误信息
app.use((err, req, res, next) => {
  res.status(err.status || 500);
  res.render("error", {
    message: err.message,
    error: {}
  });
});

app.listen(3000);

2. The following is a routing object. In the absence of promise (async/await), an exception will be thrown normally and captured in the server
xxxRouter.js

const router = require("express").Router();

router.all("/test/error", (req, res) => {
    throw new Error("我就是异常！！！");
});

But in the case of promise(async/await), an error will be reported in the console, and the capture in the server cannot be captured, resulting in q timeout

(node:30875) UnhandledPromiseRejectionWarning: Unhandled promise rejection (rejection id: 1): Error: 我就是异常！！！
(node:30875) DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

xxxRouter.js

const router = require("express").Router();

router.all("/test/error", async(req, res) => {
    throw new Error("我就是异常！！！");
});

3. In actual use, each route must try/catch and handle exceptions, which feels very redundant

// 冗余的router
router.all("/test1", async(req, res) => {
    try{
       // ...处理一些事务
       // ...各种 await
       res.end(
           // 成功返回内容
       );
    }catch(err){
        // 此处希望throw err 让server接收并处理，但是会报错
        res.end(
           // 失败返回内容
       );
    }
});
// ...之后还有很多router都要try/catch依次处理异常
=、=

Answer 1

The

async function returns a Promise 对象，这个函数中抛出的异常需要通过 Promise 对象的 catch() 或 then() for the 2nd parameter to handle.

Of course, if you want the outer function to use await，就不是用 catch() 或 then() 来处理了，而是像同步调用那样用 try ... catch ... for processing.

In my impression, Express itself does not support Promise/yield/async/await (I don’t know if the new version has developed related support). Nowadays, Koa, which has better support for Promise/yield/async/await, is generally used.

Answer 2

process.on('unhandledRejection', processErrorHandler);