NodeJS server with Bunyan

server.js

const bunyan     = require('bunyan');
const format     = require('bunyan-format');
const express    = require('express');
const bodyParser = require('body-parser')
const FS         = require('fs');
const _          = require('lodash');

global.logger = configureLogger();

const app = express();

// for logging request
const logRequest = function (req, res, next) {
  const start = new Date();
  const end   = res.end;

  res.end = function(payload, encoding){
    let responseTime = Date.now() - start.getTime();
    end.call(res, payload, encoding);
    const contentLength = Number(res.getHeader('Content-Length'));
    const _data = {
      req: _.pick(req, ['method', 'url']),
      res: _.pick(res, ['statusCode']),
      responseTime: responseTime,
      contentLength: isNaN(contentLength) ? 0 : contentLength
    }
    logger.info('%s %s %s %d %dms - %d bytes', (req.hostname || ''), _data.req.method, _data.req.url, _data.res.statusCode, _data.responseTime, _data.contentLength);    
  }
  next();
}

app.use(logRequest());
app.use(bodyParser.json());

function configureLogger(){
  const logFile = './api.LOG';
  const ws = FS.createWriteStream(logFile, { flags: 'a' });
  
  // formatting options for stdout
  const formatOut = format({ outputMode: 'short', levelInString: true, colorFromLevel: {
    20: 'blue',
    30: 'green',
    40: 'yellow',
    50: 'red',
    60: 'brightRed'
  }});
  
  
  const fileFormatter = format({outputMode: 'bunyan', level: true }, ws);
  
  const logger = bunyan.createLogger({
   name: 'API Logger', 
   level: 'debug',
   streams: [
     {
      level: 'debug',
      stream: fileFormatter
     },
     {
      level:  'info', 
      stream: fileFormatter
     },
     {
      level: 'debug', 
      stream: process.stdout
     }
   ]
  });
  
  logger.log = function (message) {
    logger.debug(message);
  }
  return logger;
}

app.listen(4044, () => { 
  logger.log("API Server Listening on PORT 4044");
});

Hi, when I run your server.js, I get an error:

// for logging request
const logRequest = function (req, res, next) {
const start = new Date();
console.log("nice");
console.log(req);
console.log(res);
const end = res.end;

In the above, it prints out req and res are both undefined. Can you help? thanks