Here's how I structure my NodeJS App.

I'll be explaining some of the reasoning behind the file structure and will also share some snippets on how do I expose some of the configs at a global level or how do I initiate a Database Connection across the app.

Folder Structure blow:

/app

├── config/

│ ├── db.conf.js

│ ├── app.conf.js

│ ├── app.keys.js

│ ├── db.keys.js

│ ├── init.js

├── database/

│ ├── Redis.database.js

│ ├── Mongo.database.js

│ ├── init.js

├── routes/

│ ├── App.routes.js

│ ├── Auth.routes.js

│ ├── Dashboard.routes.js

├── utils/

│ ├── Logger.util.js

├── middleware/

│ ├── App.middleware.js

│ ├── ErrorHandler.middleware.js

│ ├── init.js

├── models/

│ ├── User.model.js

├── controllers/

│ ├── App.controller.js

│ ├── User.controller.js

├── helpers/

│ ├── App.helper.js

├── views/

│ ├── layouts/

│ ├── partials/

│ ├── support/

│ │ ├── index.ejs

│ ├── documentation/

│ │ ├── index.ejs

│ ├── index.ejs

│ ├── about.ejs

│ ├── contact.ejs

/public

├── dist/

├── images/

│ ├── dashboard/

│ ├── auth/

│ ├── documentation/

├── sitemap.xml

/samples

├── .env.sample

├── db.conf.sample

├── app.conf.sample

├── app.keys.sample

/src

├── javascript/

├── css/

/node_modules

/server.js

/package.json

/.env

Store the configuration variables in .env (dotenv) which are necessary for configuring your application like App Port, Environment (Production, Staging, etc.). .env configuration will be available across your app as they are set globally as ENV variables.

Database

This is where you could create connections to your database(s) like Redis, MySQL, MongoDB etc.
You could then require the necessary configuration & keys to initiate a connection here. This will also make it easier for you manage everything related to your Database connection in one file, like adding listeners around successful connections, errors and disconnects, etc.

Later, these connectors could be loaded under initialization files as needed.

Routes

Usually, you could create a single Route file here to manage all your app related routes but it is recommended to create multiple route files which could be categorised like:

• Website Routes

• API Routes

• Authentication Routes

• Documentation Routes

etc. Above is more scalable as well as manageable. Here's a code sample for the above:

Utils

Your app may have several utility functions, like Logging important information, or something which are static and have no relevance to other classes/files, as opposed to Helpers (defined later in this post) which may help other classes or modules in your app.

Middleware

Your app will have several middleware functions which could be separated and initiated in a single file. These helpers could range from critical middleware like Body Parser, Global Error Handlers, Authentication Middleware, enabling CORS, Attaching Custom Headers or setting a View Engine in ExpressJS.

Models

Every Collection (if MongoDB) or a Table (if MySQL) will have a standalone model file. For eg: A collection of Users will have it's own User.model.js file which could be extended further for defining a Schema Structure for the collection, Setting Default Values in the DB or Validating the User Inputs before storing the values to Database.

Controllers

Controllers will be responsible to handle all the incoming requests to your application which will either render a page in response, may send a JSON payload or will handle other critical API related actions like POST, PUT, DELETE etc.

Controllers will further consume Models, say a User model to Create Users while registering on your website or will render the view files if static pages are requested.

Helpers

Unlike utility methods, helpers could be dynamic in nature and related to specific controllers when needed. Helpers may contain methods to parse some user posted payload, modify it before storing it to the Database, etc.

Views

You may not need this folder if you are developing an API only app or using a separate SSR library like Next. This may be useful when you are using Express View Engine like Pug or EJS.

You can further divide your views into Layouts, Pages & Partials. Where, Layouts could be shared between similar pages and a website could have multiple layouts. Lastly, partials will hold common components like Header, Footer, Sidebar etc which are needed across your web pages.

Public

As the name suggests, anything under this folder will be publicly accessible by your website users. CSS, JavaScript and Images will be a part of this folder.

Your app may use tools like Webpack and Gulp which will compile(minify, pre-process) your (S)CSS & JS files and move under the public folder which will later be linked on web pages. You could also build and output your React (or similar lib/framework) app under the dist/ folder.

Src

As App folder is responsible for handling all of the backend logic, Src folder will hold your JavaScript & CSS files if you are using SASS, ES 6 / Next which needs to be transpiled, compiled, minified and uglified before these could be served to the end users.

Src folder will further hold directories like CSS and JavaScript which could be customized as per your needs.

A simple explanation for init.js files before I close this article, init.js files will require rest of the files and export them to other files of your application, so that you need not have to require multiple files every time if you wish to consume them all.

Conclusion

I follow the above folder structure more or less in all the projects I build on Node. It works well for me and I would love to hear from you if it helps you in some way.

Eventually, you should try and modify the folder structure as per your needs and something which you find comfortable managing and scaling it in the long run.