CODEWITHSUNDEEP
node.jsimportmoduleexport
LChampo
LChampo

Reputation: 77

NodeJs - Imported variable is undefined

Consider this code snippet below which is in the A.js file.

const connection = {};

mongo_cli.connect(url, (err, db) => {
    ...
    connection['con'] = db;
});

module.exports = {
    mongo:{
        connection: connection['con'];
    }
}

I do this const database = require('./A').mongo.connection; in B.js. A and B js files are in the same directory.

Why database variable in B file is undefined ?

Upvotes: 0

Views: 896

Answers (3)

Michael Schmid
Michael Schmid

Reputation: 5007

This is a callback function:

(err, db) => {
    …
    connection['con'] = db;
}

It might get executed after the code that reads the database variable in B.js.

Upvotes: 0

Bhuvanachandu
Bhuvanachandu

Reputation: 175

U won't get undefined if the connection succeeded. so for handling that , you can try something like this.

const connection = {};
connection['con'] = null;
mongo_cli.connect(url, (err, db) => {
   ...

   connection['con'] = db;
});

module.exports = {
   mongo:{
       connection: connection['con']; // if connection failed then connection['con'] will be null.
   }
}

Upvotes: 0

Souvik Dey
Souvik Dey

Reputation: 703

That's because connection['con'] = db is in the execution context of the connect function callback. If you access connection['con'] from outside you're likely to get undefined. I suggest you to use Mongoose for such implementations. Here is a simple example:

const mongoose = require('mongoose');
const url = "your_mongodb_url";
const connect = mongoose.connect(url, {
  useNewUrlParser: true
});
connect.then((db) => {
    console.log('Database Connected');
}, (err) => {
   console.log(err);
});

Upvotes: 1

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