I have a CustomStore class, in its constructor I connect to a Mongo table. In class I have a saveToken() function that saves data in a table.

class CustomStore extends TokenStore {

    constructor(){
       
        connectDb(function(){
            console.log("Connected to db")
        });
    }

This is the connectDb() function called in the constructor

function connectDb(callback){
    let url = 'mongodb://localhost/zoho_whatsapp';
    let dbName = 'zoho_auth';

    let client = new MongoClient(url, { useNewUrlParser: true });
    client.connect((err) => {
        if (err) { throw err; }

        let db = client.db(dbName);
        let collection = db.collection('oauthtokens');

        callback(collection, client, db);
    });
}

And this is the saveToken() function

saveToken(user, token) {
        console.log("The token is saved");
    }

}

Now I want to call the function from another file

new zohoPersists.CustomStore().saveToken (user, token);

But the function ran before the constructor and I have not yet connected to the Mongo table. Do I need to write a promise function? I do not know enough ...

Thanks