I'm building a Koa.js server and need to connect to MongoDB to store and retrieve data. Here is how to do it with some simple steps:

Step 1: Connect the database before Koa app initialised

const initDB = require('./database');

initDB();

const app = new Koa();

Inside the database.js, import mongoose. You will need to npm install -save mongoose as well. It is an Object Data Modeling (ODM) library.


const mongoose = require('mongoose');
import { connexionString } from './conf/app-config';

const initDB = () => {
  mongoose.connect(connexionString);
  mongoose.connection.once('open', () => {
      console.log('connected to database');
    });
  mongoose.connection.on('error', console.error);
}

module.exports = initDB;

And the create the config of your connection string:

export const connexionString = 'mongodb+srv://'+secret.mongodb.username+':'+secret.mongodb.password+'@xxxxxx.mongodb.net/test?retryWrites=true&w=majority';

You may run a local mongodb or you can use MongoDB Altas and run it on AWS cloud. Then you would get the connection string to put inside your config file.

Step 2: Create a schema in Koa

For example, we create a user schema inside /models/users.js


const mongoose = require('mongoose');
const Schema = mongoose.Schema;

const UserSchema = new Schema({
  username: String,
  email: String,
  picture: String
});

module.exports = mongoose.model('User', UserSchema);

Step 3: Create a service to query the data

For example, we have a /service/user.service.js

import User from '../models/users';

export const getUserFromDb = async (username) => {
  const data = await User.findOne({username: username})
  return data;

};

export const createUserInDb = async (user) => {
  var newUser = new User(user);
  newUser.save();
  return user;

}

Step 4: Call the service in Koa controller

For example, we have a /controller/user.controller.js

import { getUserFromDb } from '../service/user.service';
import { createUserInDb } from '../service/user.service';


  static async getUser(ctx) {
    const user = await getUserFromDb(ctx.query.username);
    ctx.body = user;
  }

  static async registerUser(ctx) {
    const user = await createUserInDb(ctx.request.body);
    ctx.body = user;
  }

Finally you can register the route using the controller and you can see the data being stored in the database. Let me know if you have any questions.