var express = require('express'); 
var app = express(); 
var PORT = 3000; 

const bodyParser = require('body-parser')
app.use(bodyParser.json())
app.use(bodyParser.urlencoded({extended: true}));
 
app.post('/', function (req, res) { 
  console.log(req.body); 
  console.log(req.body.username);
  res.end(); 
}); 

app.listen(PORT, function(err){ 
  if (err) console.log(err); 
  console.log("Server listening on PORT", PORT); 
});

Test by postman: Post: http://localhost:3000 { "username":"userabc", "password":"passwd1234" }

But, the result is: {} undefined