<\/path>\n\t\t\t<\/svg>\n\t\t<\/button><\/figure>\n<\/div>Modular architecture is a software design approach that divides an application into independent, self-contained modules. Each module represents a specific feature or business capability and contains the components required to support that functionality.<\/p>
Every NestJS application contains at least one root module, while larger applications are composed of multiple feature modules that work together.<\/p>
Each module serves as a boundary for a specific area of the application. Related functionality stays inside the same module, allowing features to be separated into distinct parts of the codebase.<\/p>
Common examples include authentication, user management, payment, and notification modules. An authentication module provides functionality for user authentication and access control, while a payment module handles transaction processing and payment provider integrations.<\/p>
As applications grow, additional features are introduced as new modules. Each module focuses on a specific responsibility and becomes part of the overall application structure.<\/p>
The module system provides the framework that organizes a NestJS application. Once functionality is divided into modules, NestJS uses controllers and application logic inside those modules to handle incoming requests and generate responses.<\/p>
TypeScript support<\/h3>
NestJS uses TypeScript as a first-class development feature. The framework is built with TypeScript and uses its type system throughout application development, making typed controllers, services, and other application components a standard part of the development workflow.<\/p>
TypeScript helps define clear contracts between different parts of an application. Interfaces describe the structure of data, while decorators provide metadata that NestJS uses to configure routes, modules, providers, and other framework features. <\/p>
Together, these tools create a more consistent development experience across the codebase.<\/p>
Modern development tools also benefit from TypeScript integration. Editors can provide autocomplete suggestions, parameter hints, navigation features, and code analysis based on type information. <\/p>
Developers can inspect services, controllers, and data structures more efficiently while working on larger projects.<\/p>
Type checking helps identify errors before the application runs. Mismatched data types, missing properties, and incorrect method usage can be detected during development, reducing the likelihood of runtime issues and making code changes easier to verify.<\/p>
TypeScript also helps maintain consistency as applications grow. Shared types, interfaces, and application contracts make it easier for multiple developers to work within the same codebase while following the same data structures and development patterns.<\/p>
Although TypeScript is the default choice, NestJS also supports standard JavaScript projects. Developers can use the framework without TypeScript, while still benefiting from the same application architecture and framework features.<\/p>
What are NestJS’s core building blocks?<\/h2>
NestJS applications are assembled from reusable building blocks that each serve a specific purpose. <\/p>
Services contain business logic, providers manage shared functionality, and dependency injection connects application components without creating tight coupling. <\/p>
Services<\/h3>
Services are reusable classes that contain backend business logic in a NestJS application. A service handles the work that should not live directly inside a controller, such as validating data, calculating values, querying a database, or sending an email.<\/p>
Controllers receive requests and delegate tasks to services. For example, an authentication controller might receive a login request, then call a user validation service to check credentials. <\/p>
A payment controller can receive a checkout request, then call a payment service to calculate totals, apply discounts, and prepare the transaction.<\/p>
Separating logic into services keeps controllers focused on request handling. Controllers define the route, read request data, and return a response, while services implement the application rules that drive that request.<\/p>
Services also help avoid duplicated backend logic. If user validation is needed during login, registration, and profile updates, the same validation service can support all three workflows. <\/p>
If email sending is required after checkout, password reset, and account verification, a single email service can handle those actions from a single location.<\/p>
Database operations are commonly implemented within services as well. An order service can create new orders, retrieve order history, update order status, and coordinate related database queries. <\/p>
Keeping data access close to business logic gives each feature a clear place for processing and persistence.<\/p>
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