This backend service for the calculator application is built using NestJS, which provides a robust framework for building scalable and maintainable Node.js server-side applications. The architecture focuses on modularity, testability, and adherence to modern software engineering principles.
NestJS encourages good architecture practices through its own built-in modularity features. The backend is organized into different modules to isolate concerns:
User: Manages user data and user-related functionalities.Authentication: Handles JWT-based user authentication.Calculations: Deals with the calculator's operations storing and fetching logic.
- NestJS (plus framework built-in stuff such as the validators for incoming data)
- Mongoose/MongoDB
- JWT for Authentication
- Jest
- Bcrypt for hashing
Each module in the backend lives in its own folder, which contains various related files:
*.module.ts: The main module file that brings all the related code together.*.controller.ts: Handles incoming requests and returns responses.*.service.ts: Contains the business logic and calls the repository.*.repository.ts: Directly interacts with the database.*.schema.ts: Defines the Mongoose schema for the database collection.*.dto.ts: Data Transfer Object - An object that carries data between processes.*.entity.ts: A TypeScript class that defines the object and type structure for the database records.
The *.entity.ts is particularly important because it defines the type returned by the repository layer model methods. By doing this, we avoid "leaking" database-specific types into other layers of the application, thereby reducing the coupling to the database provider.
- Run the MongoDB container:
$ docker-compose up -d- Rename
.env.exampleto.env. - To successfully run all the tests, you also have to add an
env.testfile, which can currently be a copy of the.env.example, that you renamed to.env.
$ yarn install$ yarn run start:dev# unit tests
$ yarn run test
# e2e tests
$ yarn run test:e2e
# test coverage
$ yarn run test:cov