How to get all the collections of MongoDB? - mongodb

Question

I want to get access to all the collections of my MongoDB database.
But I am unable to do so.
I am using mongoose.connection.db.getCollection(collection_name) just above the listen part of code but console is saying
mongoose.connection.db.getCollection is not a function.
Here is my code
import express from "express";
import mongoose from "mongoose";
import Messages from "./messages.js";
import dynamicModel from "./messagesRoom.js";
import cors from "cors";
// app configuration
const app = express();
const port = process.env.PORT || 9000;
//middleware
app.use(express.json());
app.use(cors());
// DB Configuration
const url = "mongodb+srv://username:password#cluster0.zp9dc.mongodb.net/Whatsapp_MERN";
mongoose.connect(url, {useCreateIndex: true, useNewUrlParser: true, useUnifiedTopology: true})
.then(()=> console.log('mongoDB is connected'))
.then(err => console.log(err));
const db = mongoose.connection;
db.once('open', () => {
console.log("DB is connected");
const msgCollection = db.collection('messagecontents');
const changeStream = msgCollection.watch();
changeStream.on('change', (change) => {
console.log(change);
if(change.operationType === 'insert'){
const msgDetails = change.fullDocument;
pusher.trigger('messages', 'inserted',
{
name: msgDetails.name,
message: msgDetails.message,
timestamp: msgDetails.timestamp,
received: msgDetails.received,
})
}
else{
console.log('Error triggering pusher');
}
})
})
// API routes
app.get("/", (req, res) => {
res.status(200).send("Hello World");
})
app.get("/messages/sync", async (req, res) => {
await Messages.find( (err, data) => {
if(err){
console.log(err);
res.status(500).send(err);
}else{
res.status(200).send(data);
}
})
})
app.post("/changeChat", (req, res) => {
const collection_name = req.body.chatName;
let collection = mongoose.connection.db.getCollection("collection_name");
console.log(collection);
})
// listening part
app.listen(port, () => console.log(`listening on port number ${port}`));
please suggest me a way using which I can get access to collections of database according to the name I am using.

Answer 1

mongoose.connection.on('open', function (ref) {
mongoose.connection.db.listCollections().toArray(function(err, names){
console.log(names)
})
})
Try this code block below "mongoose.connect()", the 'listCollections()' function will return the list of all the collection in the respective database and 'toArray()' function will convert that list into array, then we simply log the array.