Rest api with node.js

Hi fellows! Getting this nasty error.
node:159192) UnhandledPromiseRejectionWarning: TypeError: callback is not a function
at C:\Users\ddobrikov\Desktop\cashierles\node_modules\mongoose\lib\connection.js:785:13
at processTicksAndRejections (internal/process/task_queues.js:93:5)
(node:159192) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:159192) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

my code

const express = require('express'); 
const app = express(); 
const mongoose = require('mongoose'); 
const bodyParser = require('body-parser');
require('dotenv/config');


//import routes
const postsRoute = require('./routes/posts');  

app.use(bodyParser);

app.use('/posts', postsRoute); 

//routes 

app.get('/',(req, res) => { 
   res.send('We are on home');
}) 


// connect to a database
mongoose.connect(process.env.DB_CONNECTION,{ useUnifiedTopology: true }, {useNewUrlParser: true}, () => console.log('Connect to Db'));

//server 
app.listen(3000); 
const express = require('express'); 
const router  = express.Router();  
const Post = require('../models/Post');

router.get('/',(req, res) => { 
    res.send('We are on posts');
})   

router.get('/specific',(req, res) => { 
    res.send('We are on admin');
})  


router.post('/',(req, res) => { 
    console.log(req.body);
}) 
module.exports= router;
`type or paste code here`

Hello!

That’s because the mongoose.connect accepts only three parameters.

Even if delete the function and leave three parameters still getting the error. Have you got another idea why getting it?

You should review the following challenge which shows the proper syntax for mongoose.connect. You are close, but you have made a small mistake. What is the 2nd argument supposed to be?

https://www.freecodecamp.org/learn/apis-and-microservices/mongodb-and-mongoose/install-and-set-up-mongoose