The readiness status of the mongoose connection is resulting in a TypeError: Unable to access undefined properties (reading 'readyState')

Question

The readiness status of the mongoose connection is resulting in a TypeError: Unable to access undefined properties (reading 'readyState')

I've been utilizing Mongo Memory Server for my unit tests successfully, but all of a sudden mongoose.connection is returning as undefined. This has left me completely baffled! I would have anticipated readyState to at least be 0.

import * as mongoose from 'mongoose';
import { MongoMemoryServer } from 'mongodb-memory-server';

let con: mongoose.Connection;
let mongoServer: MongoMemoryServer;

export const connectToDatabase = async () => {
  mongoServer = await MongoMemoryServer.create();
  await mongoose.connect(mongoServer.getUri(), {})
    .catch((err) => {
      console.log(err); // no error is thrown
    });
    con = mongoose.connection; // Why is this turning out to be undefined?!
    console.log(con.readyState); // This line seems to be triggering the error
}

typescript mongoose mongo-memory-server

Answer 1

Answer №1

When the esModuleInterop option is set to true or unset in the tsconfig.json file, use the default import syntax import mongoose from 'mongoose'.

If the esModuleInterop option is set to false or unset, use the namespace import syntax

import * as mongoose from 'mongoose'

.

import mongoose from 'mongoose';
import { MongoMemoryServer } from 'mongodb-memory-server';

let con: mongoose.Connection;
let mongoServer: MongoMemoryServer;

export const connectDB = async () => {
  mongoServer = await MongoMemoryServer.create();
  await mongoose.connect(mongoServer.getUri(), {})
    .catch((err) => {
      console.log(err);
    });
  con = mongoose.connection;
  console.log('con.readyState: ', con.readyState);
}

connectDB();

Logs:

 ⚡  npx ts-node ./index.ts
con.readyState:  1

Package versions:

"mongodb-memory-server": "^8.12.2",
"mongoose": "^7.1.1",

Answer 2

When the esModuleInterop option is set to true or unset in the tsconfig.json file, use the default import syntax import mongoose from 'mongoose'.

If the esModuleInterop option is set to false or unset, use the namespace import syntax

import * as mongoose from 'mongoose'

.

import mongoose from 'mongoose';
import { MongoMemoryServer } from 'mongodb-memory-server';

let con: mongoose.Connection;
let mongoServer: MongoMemoryServer;

export const connectDB = async () => {
  mongoServer = await MongoMemoryServer.create();
  await mongoose.connect(mongoServer.getUri(), {})
    .catch((err) => {
      console.log(err);
    });
  con = mongoose.connection;
  console.log('con.readyState: ', con.readyState);
}

connectDB();

Logs:

 ⚡  npx ts-node ./index.ts
con.readyState:  1

Package versions:

"mongodb-memory-server": "^8.12.2",
"mongoose": "^7.1.1",

Answer 3

Answer №2

import * as mongoose from 'mongoose';
import { MongoMemoryServer } from 'mongodb-memory-server';

let connection: mongoose.Connection;
let memoryServer: MongoMemoryServer;

export const establishConnection = async () => {
  memoryServer = await MongoMemoryServer.create();
  await mongoose.connect(memoryServer.getUri(), {})
  .catch((error) => {
    console.log(error);
  });
  connection = mongoose.connections[0];
  console.log(connection.readyState);
}

To address the issue, I made a change by replacing "mongoose.connection" with "mongoose.connections[0]" as shown in the code snippet above. It's still unclear whether this is related to an aspect of mongoose version 7.2.0 or is specific to my local development environment setup.

Answer 4

import * as mongoose from 'mongoose';
import { MongoMemoryServer } from 'mongodb-memory-server';

let connection: mongoose.Connection;
let memoryServer: MongoMemoryServer;

export const establishConnection = async () => {
  memoryServer = await MongoMemoryServer.create();
  await mongoose.connect(memoryServer.getUri(), {})
  .catch((error) => {
    console.log(error);
  });
  connection = mongoose.connections[0];
  console.log(connection.readyState);
}

To address the issue, I made a change by replacing "mongoose.connection" with "mongoose.connections[0]" as shown in the code snippet above. It's still unclear whether this is related to an aspect of mongoose version 7.2.0 or is specific to my local development environment setup.

The readiness status of the mongoose connection is resulting in a TypeError: Unable to access undefined properties (reading 'readyState')

Answer №1

Answer №2

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