嗨，请找到答案

const express = require('express');
const app = express();
const port = 8080;

app.get('/', (req, res) => res.send('Hello home!'));
app.get('/about-us', (req, res) => res.send('Hello about us!'));
app.post('/user/set-profile', (req, res) => res.send('Hello profile!'));
//last 404 page 
app.get('*', (req, res) => res.send('Page Not found 404'));
app.listen(port, () => console.log(`Example app listening on port ${port}!`));

在某些情况下，404页面不能被写入并作为最后一个路由执行，特别是如果您有一个异步路由功能，从而引入了一个迟到的/路由。在这些情况下可以采用下面的模式。

var express = require("express.io"),
    app = express(),
    router = express.Router();

router.get("/hello", function (req, res) {
    res.send("Hello World");
});

// Router is up here.
app.use(router);

app.use(function(req, res) {
    res.send("Crime Scene 404. Do not repeat");
});

router.get("/late", function (req, res) {
    res.send("Its OK to come late");
});

app.listen(8080, function (){
    console.log("Ready");
});

我认为你应该首先定义你所有的路线，然后作为最后的路线添加

//The 404 Route (ALWAYS Keep this as the last route)
app.get('*', function(req, res){
  res.status(404).send('what???');
});

一个示例应用程序的工作:

app.js:

var express = require('express'),
    app = express.createServer();

app.use(express.static(__dirname + '/public'));

app.get('/', function(req, res){
  res.send('hello world');
});

//The 404 Route (ALWAYS Keep this as the last route)
app.get('*', function(req, res){
  res.send('what???', 404);
});

app.listen(3000, '127.0.0.1');

alfred@alfred-laptop:~/node/stackoverflow/6528876$ mkdir public
alfred@alfred-laptop:~/node/stackoverflow/6528876$ find .
alfred@alfred-laptop:~/node/stackoverflow/6528876$ echo "I don't find a function for that... Anyone knows?" > public/README.txt
alfred@alfred-laptop:~/node/stackoverflow/6528876$ cat public/README.txt 

.
./app.js
./public
./public/README.txt

alfred@alfred-laptop:~/node/stackoverflow/6528876$ curl http://localhost:3000/
hello world
alfred@alfred-laptop:~/node/stackoverflow/6528876$ curl http://localhost:3000/README.txt
I don't find a function for that... Anyone knows?

如果您使用express-generator包:

下(err);

这段代码将您发送到404中间件。

https://github.com/robrighter/node-boilerplate/blob/master/templates/app/server.js

这就是node-boilerplate所做的。

Express-error-handler允许您为错误指定自定义模板、静态页面或错误处理程序。它还做了其他有用的错误处理，每个应用程序都应该实现，比如防止4xx错误DOS攻击，以及在不可恢复错误时优雅地关闭。以下是你如何做到你所要求的:

var errorHandler = require('express-error-handler'),
  handler = errorHandler({
    static: {
      '404': 'path/to/static/404.html'
    }
  });

// After all your routes...
// Pass a 404 into next(err)
app.use( errorHandler.httpError(404) );

// Handle all unhandled errors:
app.use( handler );

或者对于自定义处理程序:

handler = errorHandler({
  handlers: {
    '404': function err404() {
      // do some custom thing here...
    }
  }
}); 

或者对于自定义视图:

handler = errorHandler({
  views: {
    '404': '404.jade'
  }
});