express-middlewares.js

const express = require('express');

const app = express();

// app.use === generic, will be called for every request
app.use((req, res, next) => {
  console.log(req.originalUrl, 'Time:', new Date());
  req.time = new Date();
  next();
});

// app.get === specific, will be called for every GET request that matches the path
// Why don't we call next here???
app.get('/', (req, res, next) => {
  res.json({
    message: 'Hello World!'
  });
});

app.post('/things/:id', (req, res, next) => {
  if(req.params.id == 42) {
    res.json({
      message: 'The answer'
    });
  } else {
    next(new Error('You are wrong.'));
  }
});

// HAS TO BE THE LAST MIDDLEWARE!!!
app.use((req, res, next) => {
  res.status(404);
  next(new Error('Not found.'));
});

app.use((error, req, res, next) => {
  res.json({
    message: error.message,
    stack: process.env.NODE_ENV == 'production' ? {} : error.stack
  });
});

const port = process.env.PORT || 3000;
app.listen(port, () => {
  console.log(`Listening on port ${port}`);
});