MangoDB Compass can not connect to my backend using TypeORM

I am trying to create a simple web application where I can diplay users from a MongoDB database on a React web application. However I am stuck on a problem with TypeORM and my MongoDB database. Indeed, my backend repository can not access to the database.

Here is my package.json file :

{
  "name": "backend",
  "version": "1.0.0",
  "main": "index.js",
  "scripts": {
    "build": "tsc",
    "dev": "nodemon index.ts",
    "start": "node ./dist/index.js",
    "typeorm": "ts-node -r tsconfig-paths/register ./node_modules/.bin/typeorm",
    "migration:generate": "npm run typeorm -- migration:generate --config src/config/ormconfig.json --connection  --name ",
    "migration:run": "npm run typeorm -- migration:run"
  },
  "license": "UNLICENSED",
  "dependencies": {
    "cors": "^2.8.5",
    "dotenv": "^16.0.3",
    "express": "^4.18.2",
    "mongodb": "^3.6.0",
    "typeorm": "^0.3.11"
  },
  "devDependencies": {
    "@types/cors": "^2.8.13",
    "@types/express": "^4.17.14",
    "@types/mongodb": "^4.0.7",
    "@types/node": "^18.11.8",
    "nodemon": "^2.0.20",
    "ts-node": "^10.9.1",
    "typescript": "^4.8.4"
  }
}

Here is my connectionService.ts file, which is supposed to create the connection to the database :

import { DataSource, DataSourceOptions } from "typeorm"
import { Utilisateurs } from "../entities/utilisateurs";

class connectionServices{
    public myDataSource:DataSource;


    constructor(dbConfig: DataSourceOptions){
        this.myDataSource = new DataSource(dbConfig)
    }
    public async getUsers (){
        const myusers = this.myDataSource.getMongoRepository(Utilisateurs);
        const data = await myusers.find({});
        console.log (data);
        return data;
      }
}

export default (connectionServices);

Here is my index.ts file :

import express from 'express';
import cors from 'cors';
import connectionServices from "./service/connectionService";


function main() {
 
const app = express();
const service = new connectionServices({
  type: "mongodb",
  url: "mongodb://localhost:27017",
  port: 27017,
  database: "users",
  synchronize: true,
  entities: [ 
    "src/entities/**/*.ts" 
 ],
});

app.use(cors())
 
app.get('/users/:id', function (req, res, next) {
  res.json({msg: 'This is CORS-enabled for all origins!'})
})
 
app.listen(80, function () {
  console.log('CORS-enabled web server listening on port 80')
})

app.get('/', (req, res) => {
    res.send('Well done!');
})

app.listen(4321, () => {
    console.log('The application is listening on port 4321!');
})

app.get('/users', (req,res) => {
    res.send(service.getUsers());
})

}

main();

And finally here is my ormconfig.json file :

{ 
   "type": "mongodb", 
   "host": "localhost",
   "url": "mongodb://localhost:27017",
   "port": 27017, 
   "database": "test", 
   "synchronize": true, 
   "logging": false, 
   "entities": [ 
      "src/entity/**/*.ts" 
   ], 
   "migrations": [ "src/migration/**/*.ts" 
   ], 
   "subscribers": [ "src/subscriber/**/*.ts" 
   ], 
   "cli": { 
      "entitiesDir": "src/entity", "migrationsDir": "src/migration", "subscribersDir": "src/subscriber" 
   } 
}

The backend builds and launches properly :

However when I type in the url http://localhost:4321/users, I get this error in my terminal and the backend crashes :

I have tried to put the url of the data base, or put the parameter "host": "localhost" with the correct port but nothing worked.

I have looked on several tutorials, videos without success... If someone sees the solution to my problem that would be great!

Solution

In fact the problem was in the index.ts file and in the connectionService.ts file.

In the service, it was missing a function in order to connect to the data base :

import { createConnection, DataSource, DataSourceOptions } from "typeorm"
import { Utilisateurs } from "../entities/utilisateurs.entity";

class connectionServices{
    public myDataSource:DataSource;

    async connect(){
        await this.myDataSource.connect();
    }

    constructor(dbConfig: DataSourceOptions){
        this.myDataSource = new DataSource(dbConfig);
    }
    public async getUsers (){
        const myusers = this.myDataSource.getMongoRepository(Utilisateurs);
        const data = await myusers.find({});
        console.log (data);
        return data;
      }
}

export default (connectionServices);

And in the index.ts file, I was calling the promise of a table containing the date, and not the data. Here is the working file :

import express from 'express';
import cors from 'cors';
import connectionServices from "./service/connectionService";
import { Utilisateurs } from './entities/utilisateurs.entity';


async function main() {
const app = express();
const service = new connectionServices({
  type: "mongodb",
  host: "localhost",
  port: 27017,
  database: "users",
  synchronize: true,
  entities: [ 
    Utilisateurs
 ],
});

await service.connect();

app.use(cors())
 
app.get('/users/:id', function (req, res, next) {
  res.json({msg: 'This is CORS-enabled for all origins!'})
})
 
app.listen(80, function () {
  console.log('CORS-enabled web server listening on port 80')
})

app.get('/', (req, res) => {
    res.send('Well done!');
})

app.listen(4321, () => {
    console.log('The application is listening on port 4321!');
})

app.get('/users', async(req,res) => {
    res.send(await service.getUsers());
})

}

main();

With these modifications, everything works properly.