got an error in Unhandled promise rejection

Question

I got an error in vscode terminal while I am trying to post a form in my localhost. I am using mongodb for database for my website. Below are my app.js code-

const express = require("express");
const path = require("path"); 
const bodyparser = require("body-parser");
const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/contactdance', {useNewUrlParser: true, useUnifiedTopology: true});

        const app = express();
const port = 8000;

//DEFINE MONGOOSE SCHEMA
const contactSchema = new mongoose.Schema({
    name: String,
    phone: String,
    email: String,
    address: String,
    desc: String
  });

  const contact = mongoose.model('Contact', contactSchema);

// EXPRESS SPECIFIC STUFF
app.use('/static', express.static('static')) // For serving static files
app.use(express.urlencoded())

// PUG SPECIFIC STUFF
app.set('view engine', 'pug') // Set the template engine as pug
app.set('views', path.join(__dirname, 'views')) // Set the views directory
 
// ENDPOINTS
app.get('/', (req, res)=>{ 
    const params = { }
    res.status(200).render('home.pug', params);
})

app.get('/contact', (req, res)=>{ 
    const params = { }
    res.status(200).render('contact.pug', params);
})

app.post('/contact', (req, res)=>{ 
    var myData = new contact(req.body);
    myData.save().then(()=>{
        res.send("This item has been saved successfully")
    }).catch(()=>{
        res.status(400).send("Item has not been saved")
    });

    
    // res.status(200).render('contact.pug');
});

// START THE SERVER
app.listen(port, ()=>{
    console.log(`The application started successfully on port ${port}`);
});

Below are the errors while trying to post the form-

(node:15248) UnhandledPromiseRejectionWarning: MongooseServerSelectionError: connect ECONNREFUSED 127.0.0.1:27017
    at NativeConnection.Connection.openUri (E:\program files\rr\Web Development\dance_website\node_modules\mongoose\lib\connection.js:803:32)
    at E:\program files\rr\Web Development\dance_website\node_modules\mongoose\lib\index.js:342:10
    at E:\program files\rr\Web Development\dance_website\node_modules\mongoose\lib\helpers\promiseOrCallback.js:31:5
    at new Promise (<anonymous>)
    at promiseOrCallback (E:\program files\rr\Web Development\dance_website\node_modules\mongoose\lib\helpers\promiseOrCallback.js:30:10)
    at Mongoose.connect (E:\program files\rr\Web Development\dance_website\node_modules\mongoose\lib\index.js:341:10)
    at Object.<anonymous> (E:\program files\rr\Web Development\dance_website\app.js:5:10)
    at Module._compile (internal/modules/cjs/loader.js:1015:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1035:10)
    at Module.load (internal/modules/cjs/loader.js:879:32)
    at Function.Module._load (internal/modules/cjs/loader.js:724:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:60:12)
    at internal/main/run_main_module.js:17:47
(node:15248) 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(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:15248) [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.

Below are my package.json-

{
  "name": "dance_website",
  "version": "1.0.0",
  "description": "This is a website for a polular dance academy",
  "main": "app.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "Harry bhai",
  "license": "ISC",
  "dependencies": {
    "body-parser": "^1.19.0",
    "express": "^4.17.1",
    "mongoose": "^5.10.11",
    "pug": "^3.0.0"
  },
  "devDependencies": {}
}

I opened three terminal in my vscode-

1. for nodejs

2. for mongod

3. for mongo but when I open mongo in the terminal I got an error. Below are the errors-

   MongoDB shell version v4.4.1 connecting to: mongodb://127.0.0.1:27017/?compressors=disabled&gssapiServiceName=mongodb Error: couldn't connect to server 127.0.0.1:27017, connection attempt failed: SocketException: Error connecting to 127.0.0.1:27017 :: caused by :: No connection could be made because the target machine actively refused it. : connect@src/mongo/shell/mongo.js:374:17 @(connect):2:6 exception: connect failed exiting with code 1

Answer 1

The two errors you received mean the same thing: your MongoDB server is not running.

Double-check the installation instructions for mongo itself, not for mongoose or the mongo shell.

When a machine, in your own 127.0.0.1 machine, "refuses" a connection with ECONNREFUSED, it means no server is listening on the particular port. in your case 27017. It's possible you have other configuration issues, but you certainly have that one.

You can hit http://localhost:28017 with a web browser to see whether your server is running as well.