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Express + Mongoose MongoDB Connection Configuration Sample Code

#mongodb
Tadashi Shigeoka ·  Sat, January 11, 2020

I’ll introduce sample code for MongoDB connection configuration with Express + Mongoose.

mongoose | マングース

Background

I’ll explain following the commits of Express + Mongoose demo app · Pull Request #11 · codenote-net/expressjs-sandbox that I implemented.

[Prerequisites] Node.js, MongoDB, and library versions

  • Node.js 12.14.0
  • Express 4.17.1
  • Mongoose 5.8.3
  • MongoDB 4.2.2

MongoDB started with Docker

docker run -d \\
--name mongo4.2.2 \\
-p 27017:27017 \\
mongo:4.2.2

Sample Code for Connecting to MongoDB with Express + Mongoose

Install Mongoose

npm install mongoose --save

Reference commit: npm install mongoose —save | 061c68f

MongoDB Connection Configuration with Mongoose

app.js

const mongoose = require('mongoose')

mongoose.connect(process.env.MONGODB_URL,
  {
    useNewUrlParser: true,
    useUnifiedTopology: true
  }
)
const db = mongoose.connection
db.on('error', console.error.bind(console, 'MongoDB connection error:'))
db.once('open', () => console.log('MongoDB connection successful'))

Reference commit: Setup mongoose.connect() | 28371f7

Reference articles:

Set Environment Variable MONGODB_URL with .envrc

Since it would be tedious to specify the environment variable MONGODB_URL every time you run node start, I added the following .envrc to manage environment variables with direnv.

.envrc

export MONGODB_URL=mongodb://localhost:27017/expressjs-sandbox

Reference commit: Add .envrc to gitignore for using direnv | fa1c8e3 Reference commit: Add .env.sample for committing to git repository | 8df02f0

Define Mongoose Schema and Model

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

const ArticleSchema = new Schema({
  title: {
    type: String
  },
  body: {
    type: String
  }
}, {
  timestamps: true
})

mongoose.model('Article', ArticleSchema)

Reference commit: Add the article mongoose model | 3912b3a

Mongoose Models Auto-loading Configuration

To execute all mongoose.model() at app.js startup and auto-load models, I require() all .js files under the models directory as follows.

const fs = require('fs')
const join = require('path').join

const models = join(__dirname, 'models')
fs.readdirSync(models)
  .filter(file => ~file.search(/^[^.].*\\.js$/))
  .forEach(file => require(join(models, file)))

Reference commit: Bootstrap models | e9d9035

Using Mongoose Model.find(), Model.create() in Express

Finally, please check the sample code using Mongoose Model.find(), Model.create() from Express routes/* directly at the following URL. This is only the happy path code, and error handling is omitted.

Reference commit: (DEMO) Mongoose Model.find(), Model.create() in Express routes | 3f32fff

That’s all about configuring MongoDB connection with Express + Mongoose from the Gemba.

Reference Information