server.js

#!/usr/bin/env node

'use strict';

const app = require('./app');
const http = require('http');

const port = normalizePort(process.env.PORT || '3000');
app.set('port', port);

const server = http.createServer(app);

server.listen(port);
server.on('error', onError);
server.on('listening', onListening);

function normalizePort(val) {
  const port = parseInt(val, 10);
  if (isNaN(port)) {
    return val;
  }
  if (port >= 0) {
    return port;
  }
  return false;
}

function onError(error) {
  if (error.syscall !== 'listen') {
    throw error;
  }
  const bind = typeof port === 'string' ? `Pipe ${port}` : `Port ${port}`;
  switch (error.code) {
    case 'EACCES':
      process.stdout.write(`${bind} requires elevated privileges`);
      process.exit(1);
      break;
    case 'EADDRINUSE':
      process.stdout.write(`${bind} is already in use`);
      process.exit(1);
      break;
    default:
      throw error;
  }
}

function onListening() {
  const addr = server.address();
  const bind = typeof addr === 'string' ? `pipe ${addr}` : `port ${addr.port}`;
  process.stdout.write(`start api server... ${bind}`);
}