express error handler example

app.js

var express = require('express');
var path = require('path');
var favicon = require('serve-favicon');
var logger = require('morgan');
var cookieParser = require('cookie-parser');
var bodyParser = require('body-parser');

var index = require('./routes/index');
var users = require('./routes/users');

var app = express();

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'jade');

// uncomment after placing your favicon in /public
//app.use(favicon(path.join(__dirname, 'public', 'favicon.ico')));
app.use(logger('dev'));
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));

app.use('/', index);
app.use('/users', users);

// catch 404 and forward to error handler
app.use(function (req, res, next) {
  var err = new Error('Not Found');
  err.status = 404;
  next(err);
});

// error handler
// old
// app.use(function(err, req, res, next) {
//   // set locals, only providing error in development
//   res.locals.message = err.message;
//   res.locals.error = req.app.get('env') === 'development' ? err : {};

//   // render the error page
//   res.status(err.status || 500);
//   res.render('error');
// });

// new 
app.use((err, req, res, next) => {

  console.log(err);

  res.status(err.status || 500).send({
    message: err.message
  });

});

module.exports = app;