TypeError: Cannot read property 'on' of undefined in node js and mongoose

Question

I am getting an error when i run my application.

The error:

 MongoDB.on('error', function(err) { console.log(err.message); });
 TypeError: Cannot read property 'on' of undefined
 ...

I tried to comment that part of the code out to see if i have anymore similar errors and found another same one. ( This time the word "once" )

The code:

var mongoURI = "mongodb://localhost/chatapp";
var MongoDB = mongoose.connect(mongoURI).connection;
MongoDB.on('error', function(err) { console.log(err.message); });
MongoDB.once('open', function() {
    console.log("mongodb connection open");
});

It would be really great if anyone could help me solve this :( I searched the internet and found nothing helpful.

SAGAR RAVAL · Accepted Answer · 2018-06-23 15:48:47Z

1

var mongoose = require('mongoose');
var mongoURI = "mongodb://localhost/chatapp";
var MongoDB = mongoose.connect(mongoURI).connection;
MongoDB.on('error', function(err) { console.log(err.message); });
MongoDB.once('open', function() {
    console.log("mongodb connection open");
});

also before running the application in your terminal type npm install mongoose --save

answered Jun 23, 2018 at 15:48

SAGAR RAVAL

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Comments

Aayush Jaiswal · Accepted Answer · 2018-06-23 13:16:15Z

0

Try this:

   const mongoose = require('mongoose');

    mongoose.connect(mongoURI);
    mongoose.connection.once('open',()=>{
        console.log('Connected to db');
    });

answered Jun 23, 2018 at 13:16

Aayush Jaiswal

111 bronze badge

3 Comments

ProgrammingNoob Over a year ago

Now it just says that "mongoURI is not defined"

Aayush Jaiswal Over a year ago

Is your local database running when your are executing the code.

Aayush Jaiswal Over a year ago

If you have'nt installed mongodb locally then you can refer to mlab, It is a kind of online mongodb, you will be provided with the mongoURI. Check it out on how to use it

Diogo Aleixo · Accepted Answer · 2018-06-23 14:18:18Z

0

The message is pretty clear. MongoDb is undefined.

Speaking on your MongoDb variable. Should be mongoDb with lowercase. It is one instance.

Anyway, the problem is in mongoose.connect(mongoURI).connection. Debug from there.

answered Jun 23, 2018 at 14:18

Diogo Aleixo

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Comments

oarkon · Accepted Answer · 2018-11-01 19:09:17Z

0

const config = require('../config');
const Mongoose = require('mongoose');

Mongoose.connect(config.dbURI);
Mongoose.connection.once('open',()=>{
    console.log('Connected to db');
});

it helps me.

answered Nov 1, 2018 at 19:09

oarkon

1

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