LordCrainer / nodetskeleton

A NodeJs Skeleton based in Clean Arquitecture to use TypeScript with ExpressJs, KoaJs or any other web server framework.

NodeTSkeleton

Introduction🤖

NodeTskeleton is a Clean Architecture based template project for NodeJs using TypeScript to implement with any web server framework or even any user interface.

The main philosophy of NodeTskeleton is that your solution (domain and application, “business logic”) should be independent of the framework you use, therefore your code should NOT BE COUPLED to a specific framework or library, it should work in any framework.

The design of NodeTskeleton is based in Clean Architecture, an architecture that allows you to decouple the dependencies of your solution, even without the need to think about the type of database, providersor services, the framework, libraries or any other dependencies.

NodeTskeleton has the minimum tools necessary for you to develop the business logic of your application, you can even decide not to use its included tools (you can remove them), and use the libraries or packages of your choice.

Table of contents

1. Philosophy 🧘🏽
2. Included tools 🧰
   1. Errors
   2. Locals
   3. Mapper
   4. UseCase
   5. Validator
3. Dependency injection strategy 📦
4. Using NodeTskeleton 👾
   1. Using with KoaJs 🦋
   2. Using with ExpressJs 🐛
   3. Using with another web server framework 👽
5. Infrastructure 🏗️
6. Installation 🔥
7. Run Test 🧪
8. Application debugger 🔬
9. Build for production ⚙️
10. Test your Clean Architecture 🥁
11. Coupling 🧲
12. Conclusions (Personal) 💩
13. Code of Conduct 👌
14. Warning 💀

Philosophy

Applications are generally developed to be used by people, so people should be the focus of them.

For this reason user stories are written, stories that give us information about the type of user, procedures that the user performs in a part of the application (module), important information that serves to structure the solution of our application, and in practice, how is this?

The user stories must be in the src/application path of our solution, there we create a directory that we will call modules and inside this, we create a directory for the task role, for example (customer, operator, seller, admin, ...) and inside the role we create a directory of the corresponding use case module, for example (product, order, account, sales, ...), and in practice that looks more or less like this:

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Observations 👀

• If your application has no roles, then there's no mess, it's just modules. ;)

• But taking into consideration that if the roles are not yet defined in your application, the best option would be to follow a dynamic role strategy based on permissions and each use case within the application (or use case group) would be a specific permission that would feed the strategy of dynamic roles.

• Note that you can repeat modules between roles, because a module can be used by different roles, because if they are different roles then the use cases should also be different, otherwise those users would have the same role.

• This strategy makes the project easy to navigate, easy to change, scale and maintain, which boils down to good mental health, besides you will be able to integrate new developers to your projects in a faster way.

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Included tools

NodeTskeleton includes some tools in the src/application/shared path which are described below:

Errors

Is a tool for separating controlled from uncontrolled errors and allows you to launch application errors according to your business rules, example:

throw new ApplicationError(
	resources.get(resourceKeys.PROCESSING_DATA_CLIENT_ERROR),
	error.code || applicationStatusCode.INTERNAL_SERVER_ERROR,
	JSON.stringify(error),
);

The function of this class will be reflected in your error handler as it will let you know when an exception was thrown by your system or by an uncontrolled error, as shown below:

return async function (err: ApplicationError, context: Context): Promise<void> {
	const result = new Result();
	if (err?.name === "ApplicationError") {
		console.log("Controlled application error", err.message);
	} else {
		console.log("No controlled application error", err);
	}
};

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Locals

It is a basic internationalization tool that will allow you to manage and administer the local messages of your application, even with enriched messages, for example:

import resources, { resourceKeys } from "../locals/index";

const simpleMessage = resources.get(resourceKeys.ITEM_PRODUCT_DOES_NOT_EXIST);

const enrichedMessage = resources.getWithParams(resourceKeys.SOME_PARAMETERS_ARE_MISSING, {
	missingParams: keysNotFound.join(", "),
});

// The contents of the local files are as follows:
/* 
// en: 
{
	...
	"SOME_PARAMETERS_ARE_MISSING": "Some parameters are missing: {{missingParams}}.",
	"ITEM_PRODUCT_DOES_NOT_EXIST": "The item product does not exist.",
	"YOUR_OWN_NEED": "You are the user {{name}}, your last name is {{lastName}} and your age is {{age}}.",
	...
}
// es: 
{
	...
	"SOME_PARAMETERS_ARE_MISSING": "Faltan algunos parámetros: {{missingParams}}.",
	"ITEM_PRODUCT_DOES_NOT_EXIST": "El item del producto no existe.",
	"YOUR_OWN_NEED": "Usted es el usuario {{name}}, su apellido es {{lastName}} y su edad es {{age}}.",
	...
}
...
*/

// You can add enriched messages according to your own needs, for example:
const yourEnrichedMessage = resources.getWithParams(resourceKeys.YOUR_OWN_NEED, {
	name: firstName, lastName, age: userAge
});
//

And you can add all the parameters you need with as many messages in your application as required.

This tool is now available as an NPM package.

See in NPM

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Mapper

The mapper is a tool that will allow us to change the entities to the DTOs within our application, including entity changes between the data model and the domain and vice versa.

This tool maps objects or arrays of objects, for example:

// For object
const textFeelingDto = this.mapper.mapObject<TextFeeling, TextFeelingDto>(
	textFeeling,
	new TextFeelingDto(),
);

// For array object
const productsDto: ProductDto[] = this.mapper.mapArray<Product, ProductDto>(
	products,
	() => this.mapper.activator(ProductDto),
);

Activator is the function responsible for returning a new instance for each call, otherwise you would have an array with the same object repeated N times.

This tool is now available as an NPM package.

See in NPM

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Result

result is a tool that helps us control the flow of our use cases and allows us to manage the response, be it an object, an array of objects, a message or an error as follows:

export class GetProductUseCase extends BaseUseCase {
	constructor(private productQueryService: IProductQueryService) {
		super();
	}

	async execute(idMask: string): Promise<IResult<ProductDto>> {
		// We create the instance of our type of result at the beginning of the use case.
		const result = new Result<ProductDto>();
		// With the resulting object we can control validations within other functions.
		if (!this.validator.isValidEntry(result, { productMaskId: idMask })) {
			return result;
		}
		const product: Product = await this.productQueryService.getByMaskId(idMask);
		if (!product) {
			// The result object helps us with the error response and the code.
			result.setError(
				this.resources.get(this.resourceKeys.PRODUCT_DOES_NOT_EXIST),
				this.applicationStatusCodes.NOT_FOUND,
			);
			return result;
		}
		const productDto = this.mapper.mapObject<Product, ProductDto>(product, new ProductDto());
		// The result object also helps you with the response data.
		result.setData(productDto, this.applicationStatusCodes.SUCCESS);
		// And finally you give it back.
		return result;
	}
}

The result object may or may not have a type of response, it fits your needs, and the result instance without type cannot be assigned data.

const resultWithType = new Result<ProductDto>();
// or
const resultWithoutType = new Result();

The result object can help you in unit tests as shown below:

it("should return a 400 error if quantity is null or zero", async () => {
	itemDto.quantity = null;
	const result = await addUseCase.execute(userUid, itemDto);
	expect(result.success).toBeFalsy();
	expect(result.error).toBe(
		resources.getWithParams(resourceKeys.SOME_PARAMETERS_ARE_MISSING, {
			missingParams: "quantity",
		}),
	);
	expect(result.statusCode).toBe(resultCodes.BAD_REQUEST);
});

This tool is now available as an NPM package.

See in NPM

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UseCase

The UseCase is a base class for extending use cases and if you were a retailer you could see it in action in the above explanation of the Result tool.

Its main function is to avoid you having to write the same code in every use case you have to build because it contains the instances of the common tools you will use in the case implementations.

The tools extended by this class are: the mapper, the validator, the message resources and their keys, and the result codes.

import resources, { resourceKeys, Resources } from "../locals/index";
export { IResult, Result, IResultT, ResultT } from "result-tsk";
import * as applicationStatusCodes from "../status/applicationStatusCodes.json";
import { Validator } from "validator-tsk";
import mapper, { IMap } from "mapper-tsk";

export class BaseUseCase {
  constructor() {
    this.mapper = mapper;
    this.resources = resources;
    this.validator = new Validator(
      resources,
      resourceKeys.SOME_PARAMETERS_ARE_MISSING,
      applicationStatusCode.BAD_REQUEST,
    );
  }
  mapper: IMap;
  validator: Validator;
  resources: Resources;
  resourceKeys = resourceKeys;
  applicationStatusCodes = applicationStatusCodes;
}

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Validator

The validator is a very simple but dynamic tool and with it you will be able to validate any type of object and/or parameters that your use case requires as input, and with it you will be able to return enriched messages to the client regarding the errors or necessary parameters not identified in the input requirements, for example:

/*...*/
async execute(userUid: string, itemDto: CarItemDto): Promise<IResult<CarItemDto>> {
	const result = new Result<CarItemDto>();
	if (
		!this.validator.isValidEntry(result, {
			User_Identifier: userUid,
			Car_Item: itemDto,
			Order_Id: itemDto?.orderId,
			Product_Detail_Id: itemDto?.productDetailId,
			Quantity: itemDto?.quantity,
		})
	) {
		/* 
		The error message on the result object will include a base message and will add to 
		it all the parameter names that were passed on the object that do not have a valid value.
		*/
		return result;
	}
	/*...*/
	return result;
}
/*...*/

Suppose that in the above example the itemDto object has no orderId and no quantity, then the result of the error in the object result based on the message of the SOME_PARAMETERS_ARE_MISSING for english local file would be something like this:

Some parameters are missing or not valid: Order_Id, Quantity.

Important note

In the validation process the result of messages obtained will be inserted in the {{missingParams}} key of the local message.

You can change the message, but not the key {{missingParams}}.

Validations functions (new feature 🤩)

The validation functions extend the isValidEntry method to inject small functions created for your own needs.

The philosophy of this tool is that it adapts to your own needs and not that you adapt to it.

To do this the isValidEntry function input value key pair also accepts array of small functions that must perform a specific task with the parameter to be validated.

Observation

If you are going to use the validation functions feature, you must send as a parameter an array even if it is only a function.

Important note

The validation functions should return NULL if the parameter for validate is valid and a string message indicating the reason why the parameter is not valid.

// Validator functions created to meet your own needs
function validateEmail(email: string): string {
  if (/^\w+([\.-]?\w+)*@\w+([\.-]?\w+)*(\.\w{2,3})+$/.test(email)) {
    return null;
  }
  return resources.getWithParams(resourceKeys.NOT_VALID_EMAIL, { email });
}

function greaterThan(numberName: string, base: number, evaluate: number): string {
  if (evaluate && evaluate > base) {
    return null;
  }
  return resources.getWithParams(resourceKeys.NUMBER_GREATER_THAN, {
    name: numberName,
    baseNumber: base.toString(),
  });
}

function evenNumber(numberName: string, evaluate: number): string {
  if (evaluate && evaluate % 2 === 0) {
    return null;
  }
  return resources.getWithParams(resourceKeys.MUST_BE_EVEN_NUMBER, {
    numberName,
  });
}


// So, in any use case
const person = new Person("Carl", "Sagan", 86);
/*...*/
const result = new Result();
const validEmail = "[e-mail]";
person.setEmail(validEmail);
if (!validator.isValidEntry(result, {
	Name: person.name,
	Last_Name: person.lastName,
	Age: [
		() => greaterThan("Age", 25, person.age),
		() => evenNumber("Age", person.age),
	],
	Email: [() => validateEmail(person.email)],
})) {
	return result;
};
// result.error would have the following message
// "Some parameters are missing or not valid: The number Age must be greater than 25, The Age param should be even."

This tool is now available as an NPM package.

See in NPM

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Dependency injection strategy

For dependency injection, no external libraries are used. Instead, a container strategy is used in which instances and their dependencies are created and then imported into the objects where they are to be used.

This strategy is only needed in the adapter layer for controllers, services and providers, and also for the objects used in the use case tests, for example:

// In the path src/adapters/controllers/textFeeling there is a folder called container... the index file has the following:
import { UseCaseGetHighestFeelingSentence } from "../../../../application/modules/feeling/useCases/getHighest";
import { UseCaseGetLowestFeelingSentence } from "../../../../application/modules/feeling/useCases/getLowest";
import { UseCaseGetFeeling } from "../../../../application/modules/feeling/useCases/getFeeling";
import { textFeelingService } from "../../../providers/container/index";

const getFeelingTextUseCase = new GetFeelingUsecase(textFeelingService);
const getHighestFeelingSentenceUseCase = new GetHighestFeelingSentenceUseCase(textFeelingService);
const getLowestFeelingSentenceUseCase = new GetLowestFeelingSentenceUseCase(textFeelingService);

export { getFeelingTextUseCase, getHighestFeelingSentenceUseCase, getLowestFeelingSentenceUseCase };

// The same way in src/adapters/providers there is the container folder
import TextFeelingService from "../../../application/modules/feeling/serviceContracts/textFeeling/TextFeelingService";
import TextFeelingProvider from "../../providers/feeling/TextFeelingProvider";
import { HealthProvider } from "../health/HealthProvider";

const textFeelingProvider = new TextFeelingProvider();
const textFeelingService = new TextFeelingService(textFeelingProvider);

const healthProvider = new HealthProvider();

export { healthProvider, textFeelingService };

// And your repositories (folder src/adapters/repositories) must have the same strategy

In this container the instances of the use cases for the specific controller are created and here the necessary dependencies for the operation of those use cases are injected, then they are exported and in the controller they are imported and used as following:

// For ExpressJs
import { Request, Response, NextFunction } from "../../../infrastructure/server/CoreModules";
import { TextDto } from "../../../application/modules/feeling/dtos/TextReq.dto";
import BaseController from "../BaseController";
import {
  getFeelingTextUseCase,
  getHighestFeelingSentenceUseCase,
  getLowestFeelingSentenceUseCase,
} from "./container/index";

class TextFeelingController extends BaseController {
	public constructor() {
		super();
		this.initializeRoutes();
	}
	/*...*/
	getFeelingText = async (req: Request, res: Response, next: NextFunction): Promise<void> => {
		try {
			const textDto: TextDto = req.body;
			this.handleResult(res, await getFeelingTextUseCase.execute(textDto));
		} catch (error) {
			next(error);
		}
	};
	/*...*/
}

As you can see this makes it easy to manage the injection of dependencies without the need to use sophisticated libraries that add more complexity to our applications.

But if you prefer or definitely your project need a library, you can use something like awilix or inversifyJs.

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Using NodeTskeleton

In this template is included the example code base for KoaJs and ExpressJs, but if you have a web framework of your preference you must configure those described below according to the framework.

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Using with KoaJs

Go to repo for KoaJs in this Link

And then, continue with the installation step described at the end of this manual.

Controllers

The location of the controllers must be in the adapters directory, there you can place them by responsibility in separate directories.

The controllers should be exported as default modules to make the handling of these in the index file of our application easier.

// Controller example with export default
import BaseController, { Context } from "../BaseController";
import { TextDto } from "../../../application/modules/feeling/dtos/TextReq.dto";
import {
  getFeelingTextUseCase,
  getHighestFeelingSentenceUseCase,
  getLowestFeelingSentenceUseCase,
} from "./container/index";

class TextFeelingController extends BaseController {
	public constructor() {
		super();
		this.initializeRoutes();
	}
	/*...*/
}

const instance = new TextFeelingController();
// You can see the default export
export default instance;

Example of the handling of the controllers in the index file of our application:

/*...*/
// Region controllers
import productController from "./adapters/controllers/product/Product.controller";
import shoppingCarController from "./adapters/controllers/shoppingCart/ShoppingCar.controller";
import categoryController from "./adapters/controllers/category/CategoryController";
/*...*/
// End controllers

const controllers: BaseController[] = [
	productController,
	shoppingCarController,
	categoryController,
	/*...*/
];

const app = new App(controllers);
/*...*/

Routes

The strategy is to manage the routes within the controller, this allows us a better management of these, in addition to a greater capacity for maintenance and control according to the responsibilities of the controller.

/*...*/
private initializeRoutes() {
	this.router.post("/v1/cars", authorization(), this.create);
	this.router.get("/v1/cars/:idMask", authorization(), this.get);
	this.router.post("/v1/cars/:idMask", authorization(), this.buy);
	this.router.post("/v1/cars/:idMask/items", authorization(), this.add);
	this.router.put("/v1/cars/:idMask/items", authorization(), this.remove);
	this.router.delete("/v1/cars/:idMask", authorization(), this.empty);
	/*...*/
}
/*...*/

Root path

If you need to manage a root path in your application then this part is configured in App, the infrastructure server module that loads the controllers as well:

/*...*/
private loadControllers(controllers: BaseController[]) {
	controllers.forEach((controller) => {
		// This is the line and the parameter comes from `config`.
		controller.router.prefix(config.server.root);
		this.app.use(controller.router.routes());
		this.app.use(controller.router.allowedMethods());
	});
}
/*...*/

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Using with ExpressJs

Clone this repo or use it as template, and then, continue with the installation step described in this guide.

Controllers

The location of the controllers must be in the adapters directory, there you can place them by responsibility in separate directories.

The controllers should be exported as default modules to make the handling of these in the index file of our application easier.

// Controller example with export default
import BaseController, { Request, Response, NextFunction } from "../BaseController";
import { TextDto } from "../../../application/modules/feeling/dtos/TextReq.dto";
import {
	getFeelingTextUseCase,
	getHighestFeelingSentenceUseCase,
	getLowestFeelingSentenceUseCase,
} from "./container/index";

class TextFeelingController extends BaseController {
	public constructor() {
		super();
		this.initializeRoutes();
	}
	/*...*/
}

const instance = new TextFeelingController();
// You can see the default export
export default instance;
// Or just use export default new TextFeelingController();

Example of the handling of the controllers in the index file of our application:

/*...*/
// Region controllers
import productController from "./adapters/controllers/product/Product.controller";
import shoppingCarController from "./adapters/controllers/shoppingCart/ShoppingCar.controller";
import categoryController from "./adapters/controllers/category/CategoryController";
/*...*/
// End controllers

const controllers: BaseController[] = [
	productController,
	shoppingCarController,
	categoryController,
	/*...*/
];

const app = new App(controllers);
/*...*/

Routes

The strategy is to manage the routes within the controller, this allows us a better management of these, in addition to a greater capacity for maintenance and control according to the responsibilities of the controller.

/*...*/
private initializeRoutes() {
	this.router.post("/v1/cars", authorization(), this.create);
	this.router.get("/v1/cars/:idMask", authorization(), this.get);
	this.router.post("/v1/cars/:idMask", authorization(), this.buy);
	this.router.post("/v1/cars/:idMask/items", authorization(), this.add);
	this.router.put("/v1/cars/:idMask/items", authorization(), this.remove);
	this.router.delete("/v1/cars/:idMask", authorization(), this.empty);
	/*...*/
}
/*...*/

Root path

If you need to manage a root path in your application then this part is configured in App, the infrastructure server module that loads the controllers as well:

/*...*/
private loadControllers(controllers: BaseController[]): void {
	controllers.forEach((controller) => {
		// This is the line and the parameter comes from `config`.
		this.app.use(config.server.root, controller.router);
	});
}
/*...*/

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Using with another web server framework

You must implement the configuration made with ExpressJs or KoaJs with the framework of your choice and install all the dependencies and devDependencies for your framework, You must also modify the Server module, Middleware in infrastructure directory and the BaseController and Controllers in adapters directory.

And then, continue with the step installation.

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Infrastructure

The infrastructure includes a customizable HttpClient with its response model in src/infrastructure/httpClient/TResponse.ts for error control, and at the application level a class strategy src/application/shared/result/... is included as a standardized response model.

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Installation

Depending on your need you have two options, local and with docker compose, but first of all we need to set up the .env file:

Go to project root directory, create a .env file and inside it copy and paste this content:

NODE_ENV=development
SERVER_ROOT=/api
SERVER_HOST=localhost
SERVER_PORT=3003
ORIGINS=http://localhost:3003
ENCRYPTION_KEY=JUS9192ZliRlDBWm0BmmJoZO1PbNkZt3kiXNlaGLkIT49uEdgGe79TPCbr0D
JWT_SECRET_KEY=2NtC29d33z1AF1HdPSpn

Local

First, we must install the dependencies, run:

npm install

Second, we must update the dependencies, run:

npm update

Third:

This project is configured with VS Code so if you use WindowsNT go to the next point, otherwise go to the .vscode folder and check the launch.json file according to your SO and in the tasks.json file use the lines with // for Bash and remove the lines corresponding to cmd for WindowsNT.

Finally, in any internet explorer go to:

localhost:3003/api/ping

And you can use PostMan too:

Try import this request. So, click to Import > Select Raw text, and paste the next code:

curl --location --request POST 'localhost:3003/api/v1/users/login' \
--header 'Content-Type: application/json' \
--data-raw '{
    "email": "[e-mail]",
    "password": "Tm9kZVRza2VsZXRvbg=="
}'

The password is equivalent for "NodeTskeleton" in Base64 format.

Docker Compose

The first two steps are for updating the project, but you can skip to step 3 if you prefer.

First, we must install the dependencies, run:

npm install

Second, we must update the dependencies, run:

npm update

Third, build the app with the following command:

docker-compose up -d --build

Finally, in any internet explorer go to:

localhost:3040/api/ping

And you can use PostMan too:

Try import this request. So, click to Import > Select Raw text, and paste the next code:

curl --location --request POST 'localhost:3040/api/v1/users/login' \
--header 'Content-Type: application/json' \
--data-raw '{
    "email": "[e-mail]",
    "password": "Tm9kZVRza2VsZXRvbg=="
}'

The password is equivalent for "NodeTskeleton" in Base64 format.

Observation 👀

Copies of those files launch.json and tasks.json were attached at the end of this document.

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Run Test

The tests are implemented for each use case in its respective folder.

Ideally, each use case of your application should be supported by its respective test.

The tests use the Jest library and can be run in two ways:

npm t

or

npm run test

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Application debugger

Before this maybe you should make some settings, for it you can go to Setting files

In the side menu of VS Code go to the Execute ▶ option and then at the top select the Launch via NPM option in menu and click on the green Play icon ▶️.

Remember to put some stop point in the code, for example in some method of the TextFeelingController.

For watch and debug mode, you can run the next command:

npm run watch

Nodemon This option required previous file settings Setting files

And later go to Execution and debugging option in VSCode and play to Node: Nodemon task and after select the correct process for attach to debug mode. Select some pid nodemon process like [.../bin/nodemon.js --inspect src/...]

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Build for production

To get the code you can use in a productive environment run:

npm run build

The result code will be stored in the dist directory.

You can also add your scripts in the package.json file and use them with your deployment strategies, even with docker.

To be able to debug, the system generates javascript map files in the dist directory, but this is only for testing purposes. When the build command runs, everything inside the dist directory is removed and only the necessary code is generated.

tsc

With the previous command you can also generate the code of the dist directory but this command is configured in the TS config file to generate the map files needed by the application to perform the debugging process.

Setting files

(.vscode)🛠️

This step is optional and it working for windows, but in another OS (Linux or Mac OS) you can do the next instructions:

1. Goto to left menu Depuration and Execution and create a launch.json file settings for NodeJs, do not play it yet...
2. Press combination key command Ctrl + Shift + B and select tsc: watch or tsc: build, so...
3. Now, you can play the configuration of previous one step called Launch Program.
4. So, you can ready for the action

So, for Windows, you need this files or you could also perform the above steps. They should also work for Windows.

Files for .vscode folder

// launch.json

{
  "version": "0.2.0",
  "configurations": [
    {
      "type": "node",
      "request": "launch",
      "name": "Launch via NPM",
      "program": "${workspaceFolder}/src/index.ts",
      "console": "integratedTerminal",
      "preLaunchTask": "tsc: build-tsconfig",
      "sourceMaps": true,
      "outFiles": ["${workspaceFolder}/dist/**/*.js"]
    },
		// For attach to watch mode before run command: npm run watch
		{
      "type": "node",
      "request": "attach",
      "name": "Node: Nodemon",
      "processId": "${command:PickProcess}",
      "restart": true,
      "sourceMaps": true,
      "protocol": "inspector"
    }
  ]
}

// tasks.json

{
	"version": "2.0.0",
	"tasks": [		
		{
			"type": "typescript",
			"tsconfig": "tsconfig.json",
			"problemMatcher": [
				"$tsc"
			],
			"group": {
				"kind": "build",
				"isDefault": true
			},
			"label": "tsc: build-tsconfig",
			"options": {
				"shell": {
					"executable": "cmd.exe", // With cmd...
					"args": ["/d", "/c"],
					// "executable": "C:/Program Files/Git/git-bash.exe", // or with git bash too
					// "args": ["-l", "-i"]
				}
			}
		}
	]
}

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Test your Clean Architecture

Something important is to know if we really did the job of building our clean architecture well, and this can be found very easily by following these steps:

1. Make sure you don't have any pending changes in your application to upload to your repository, otherwise upload them if you do.

2. Identify and remove adapters and infrastructure directories from your solution, as well as the index.ts file.

3. Execute the test command npm t or npm run test and the build command tsc or npm run build too, and everything should run smoothly, otherwise you violated the principle of dependency inversion or due to bad practice, application layers were coupled that should not be coupled.

4. Run the git checkout . command to get everything back to normal.

5. Most importantly, no domain entity can make use of an application service and less of a provider service (repository or provider), the application services use the entities, the flow goes from the most external part of the application to the most internal part of it.

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Coupling

For the purpose of giving clarity to the following statement we will define coupling as the action of dependence, that is to say that X depends on Y to function.

Coupling is not bad if it is well managed, but in a software solution there should not be coupling of the domain and application layers with any other, but there can be coupling of the infrastructure layer or the adapters layer with the application and/or domain layer, or coupling of the infrastructure layer with the adapters layer and vice versa.

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Conclusions

• The clean architecture allows us to develop the use cases and the domain (business logic) of an application without worrying about the type of database, web server framework, protocols, services, providers, among other things that can be trivial and that the same application during the development will tell us what could be the best choice for the infrastructure and adapters of our application.

• The clean architecture, the hexagonal architecture, the onion architecture and the ports and adapters architecture in the background can be the same, the final purpose is to decouple the business layer of our application from the outside world, basically it leads us to think about designing our solutions from the inside to outside and not from the outside to inside.

• When we develop with clean architecture we can more easily change any "external dependency" of our application without major concerns, obviously there are some that will require more effort than others, for example migrating from a NoSql schema to a SQL schema where probably the queries will be affected, however our business logic can remain intact and work for both models.

• The advantages that clean architecture offers us are very significant; it is one of the best practices for making scalable software that works for your business and not for your preferred framework.

• Clean architecture is basically based on the famous and well-known five SOLID principles that we had not mentioned until this moment and that we very little internalized.

• If you liked it and you learned something, give me my star in the project that is the way you can thank me, don't be a damn selfish person who doesn't recognize the effort of others.

Observation 👀

"The world is selfish" because I am surprised by the number of people who visit this project and browse through all its modules and files, but it seems that it is nothing new because they do not leave their star, good for them.

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Code of Conduct

The Contributor Covenant Code of Conduct for this project is based on Covenant Contributor which you can find at the following link:

• Go to Code of Conduct

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Warning

Use this resource at your own risk.

-You are welcome to contribute to this project, dare to do so.

-If you are interested you can contact me by this means.

• 📫 Write to him

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