CommonJS modules

CommonJS is the traditional Node.js module system using require() and module.exports.

Splitting an application into focused modules makes code easier to reuse, test, and maintain.

Deep dive

Why modules matter

Modules let you divide a large application into small responsibilities. For example, database code can stay in a database module while authentication logic stays in an authentication module.

Good module design

• Keep exports focused.
• Avoid circular dependencies.
• Use descriptive names.
• Keep business logic separate from HTTP-specific code when the project grows.