How do I require my custom class in Node.js?

Question

I have database.js where my Database class is.

database.js

class Database {
    constructor() {
        this.uri = "mongodb+srv: ....."
    }
    get_uri = () => {
        return this.uri
    }
    connect = async client => {
        await client.connect();
        console.log("Successfully connected!")
        return client;
    }

    disconnect = async client => {
        await client.close();
    }
}

exports.Database = new Database()

server.js

const {MongoClient} = require('mongodb');
const db = require("./server/database");
const connect = db.connect(); // TypeError: db.connect is not a function

files

server -|
        |-database.js

package.json
server.js

printed db variable for my code above

[0] Database object:
[0] {
[0]   Database: Database {
[0]     get_uri: [Function: get_uri],
[0]     connect: [AsyncFunction: connect],
[0]     disconnect: [AsyncFunction: disconnect],
[0]     uri: 'mongodb+srv:......'
[0]   }
[0] }

EDIT 1

Soulka, just done this:

const {MongoClient} = require('mongodb');
const { Database } = require("./server/database");
const connect = Database.connect();

and still TypeError: Cannot read property 'connect' of undefined

But it raises an error, which I put as a comment above. What I am doing wrong?

Thank you!

your file ist Database.js not database.js. use const db = require("./server/Database"); Also your db.connect() is an async function. You might want to await it. — SoulKa
– SoulKa, Commented Feb 4, 2021 at 9:00

SoulKa · Accepted Answer · 2021-02-04 09:23:26Z

1

Your import should be const { Database } = require("./server/database"); instead of const db = require("./server/database");

This is because you are exporting via exports.Database = .. not exports = ...

EDIT (for your edit): I'm not sure if it makes a difference, but you should think about using a singleton like this:

class Database {
    constructor() {
        this.uri = "mongodb+srv: ....."
    }

    static get instance() {
        if (!Database._instance) Database._instance = new Database();
        return Database._instance;
    }

    get_uri = () => {
        return this.uri
    }
    connect = async client => {
        await client.connect();
        console.log("Successfully connected!")
        return client;
    }

    disconnect = async client => {
        await client.close();
    }
}

exports.Database = Database

And then in server.js

const {MongoClient} = require('mongodb');
const { Database }= require("./server/database");
const db = Database.instance;
const connect = db.connect( someClientMustGoHere ); // <---- THIS LINE

EDIT 2: Fixed the last line of server.js to be const connect = db.connect( someClientMustGoHere );

edited Feb 4, 2021 at 9:23

answered Feb 4, 2021 at 9:03

SoulKa

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2 Comments

WhoAmI Over a year ago

About bold edit - still ` Cannot read property 'connect' of undefined, and printed db variable` is same

SoulKa Over a year ago

you are forgetting to pass the client to the connect( client ) function! It must be db.connect( someClient ); Maybe assign the client to the Database instance so it can be accessed via this.client?

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