node.js - Express js error handling

Question

I'm trying to get error handling running with express but instead of seeing a response of "error!!!" like I expect I see "some exception" on the console and then the process is killed. Is this how error handing is supposed to be setup and if so is there another way to catch errors?

var express = require('express');
var app = express();

app.use(function(err, req, res, next) {
    console.log("error!!!");
    res.send("error!!!");
});

app.get('/', function(request, response) {
    throw "some exception";
    response.send('Hello World!');
});

app.listen(5000, function() {
  console.log("Listening on 5000");
});

Answer 1

An example app/guide on error handling is available at https://expressjs.com/en/guide/error-handling.html However should fix your code:

// Require Dependencies
var express = require('express');
var app = express();

// Middleware
app.use(app.router); // you need this line so the .get etc. routes are run and if an error within, then the error is parsed to the next middleware (your error reporter)
app.use(function(err, req, res, next) {
    if(!err) return next(); // you also need this line
    console.log("error!!!");
    res.send("error!!!");
});

// Routes
app.get('/', function(request, response) {
    throw "some exception";
    response.send('Hello World!');
});

// Listen
app.listen(5000, function() {
  console.log("Listening on 5000");
});