Ex⚡

Overview 🌟

exutile is a lightweight utility library designed specifically for Express.js, helping developers simplify server-side logic and reduce boilerplate code. It provides ready-to-use features like error handling, HTTP status utilities, and standardized API responses, enabling you to write cleaner, more maintainable code effortlessly.

Table of Contents 📚

• Features
• Installation
• Motivation
• Quick Start
• globalErrorHandler: Error Handler Middleware
• async-handler: Simplifying Controllers
• Standardized JSON Responses with ApiRes
• Standardized HttpError
• Standardized HttpStatus
• Permission makePermission function
• proxyWrapper: Class Controllers
• Conclusion
• Contributing
• Author
• License

Features ✨

• ✅ Simplified error handling with globalErrorHandler
• ✅ Automatic async error handling using async-handler
• ✅ Standardized API responses with ApiRes
• ✅ Flexible HTTP status codes and custom error classes
• ✅ Class-based controllers with proxyWrapper

Motivation 💡

Building APIs often involves repetitive tasks like handling errors, managing HTTP status codes, or structuring JSON responses. exutile was created to eliminate this hassle, allowing developers to focus on writing business logic instead of reinventing common solutions. Whether you're a beginner or an experienced developer, exutile streamlines your workflow and ensures your Express applications are consistent and reliable.

Installation 📥

npm install --save exutile

Quick Start ⚡

Here’s a minimal setup to get you started with exutile:

import express from 'express';
import {handler, globalErrorHandler} from 'exutile';

const app = express();

// Middleware
app.use(express.json());

// Example route using async-handler
const getUser = handler(async (req, res) => {
  const user = await getUserById(req.params.id);
  return ApiRes.ok(user); // Send user data in the response
});

// Routers
app.get('/user/:id', getUser);

// Error handling middleware
app.use(
  globalErrorHandler({
    isDev: process.env.NODE_ENV === 'development',
    write: error => console.error(error),
  }),
);

app.listen(3000, () => {
  console.log('Server running on port 3000');
});

globalErrorHandler: Error Handler Middleware 🚨

The globalErrorHandler middleware manages HttpErrors and Unknown errors, returning appropriate json responses.

Usage:

import {errorHandler} from 'exutile';

// Basic usage with default options
app.use(
  globalErrorHandler({
    isDev: process.env.NODE_ENV === 'development',
  }),
);

// Custom usage with logging in production mode
app.use(
  globalErrorHandler({
    isDev: process.env.NODE_ENV === 'development',
    write: error => console.error(error),
  }),
);

Signature:
globalErrorHandler({ isDev: boolean, write?: (err) => void }): ErrorRequestHandler

Options:

• isDev: Enables detailed error messages in development mode (default: true).
• write: Optional callback for logging or handling errors.

async-handler: Simplifying Controllers 🛠️

Eliminates repetitive try-catch blocks by managing error handling for both async and sync functions. It also integrates seamlessly with ApiRes for enhanced response handling.

Simplifying Route Handlers

import {handler, ApiRes} from 'exutile';

// Route without async-handler (traditional approach with try-catch)
app.get('/user/:id', async (req, res, next) => {
  try {
    const user = await getUserById(req.params.id);
    res.status(200).json(user);
  } catch (error) {
    next(error); // Pass the error to the error-handling middleware
  }
});

// Route using handler (simplified with exutile)
app.get(
  '/user/:id',
  handler(async (req, res) => {
    const user = await getUserById(req.params.id); // Fetch user from database
    return ApiRes.ok(user, 'User fetched successfully'); // Send success response using ApiRes
  }),
);

Advanced Example: Handling Cookies and Headers

import {handler, Handler} from 'exutile';

// Login type handler
type LoginInput = InputType<{email: string; password: string}>;

// Login request handler
const login = handler<LoginInput>(async (req, res) => {
  const {email, password} = req.body;
  const user = await loginUser(email, password);

  // Manually setting headers
  res.setHeader('X-Custom-Header', 'SomeHeaderValue');

  // Set multiple cookies for authentication
  res.cookie('access-token', user.accessToken, {
    httpOnly: true,
    secure: true, // Set to true in production with HTTPS
    maxAge: 3600000, // 1 hour
  });

  res.cookie('refresh-token', user.refreshToken, {
    httpOnly: true,
    secure: true,
    maxAge: 7 * 24 * 3600000, // 1 week
  });

  // API response with token and user info
  return ApiRes.ok(user, 'Logged in successfully');
});

Minimal Examples

• Simple Response:

const getHome = handler(() => 'Hello World!');

• Custom JSON Response:

const getHome = handler(() => ({message: 'Hello World!'}));

• Without ApiRes:

const login = handler(async (req, res) => {
  const user = await getUserById(req.params.id);
  // Manually setting headers
  res.setHeader('X-Custom-Header', 'SomeHeaderValue');
  // Setting cookies
  res.cookie('access-token', user.accessToken, {
    httpOnly: true,
    secure: true, // Set to true in production with HTTPS
    maxAge: 3600000, // 1 hour
  });
  // Sending a custom JSON response
  return res.status(200).json({
    status: 'success',
    message: 'User fetched successfully',
    data: user,
  });
});

Middleware Example: Role-Based Access Control

import {Role} from './constants';
import {handler, ForbiddenError} from 'exutile';

/** Permission middleware */
export const permission = (...roles: Role[]) =>
  handler(async (req, _, next) => {
    const {user} = req;

    if (!roles.includes(user?.role)) throw new ForbiddenError(`Access denied for ${req.originalUrl}`);

    next();
  });

export const onlyAdmin = permission(Role.ADMIN);
export const adminOrUser = permission(Role.ADMIN, Role.USER);

Standardized JSON Responses with ApiRes 📊

ApiRes provides a consistent structure for API responses. It includes several static methods that handle common response patterns, such as ok, created, and paginated.

Usage:

import {ApiRes} from 'exutile';

// Example without async-handler
app.get('/hello', (req, res) => new ApiRes.ok({}, 'Hello World').toJson(res));

// With paginated
const list = handler(async req => {
  const {data, meta} = await getUsers(req.query);
  return ApiRes.paginated(data, meta, 'Get users list successfully');
});

// With created
const create = handler(async req =>
  ApiRes.created(await createUser(req.body), 'User created successfully');
);

// With ok
const get = handler(async req =>
  ApiRes.ok(await getUser(req.params), 'Get user successfully');
);

// Routers
app.route('/').get(list).post(create);
app.route('/:id').get(get);

ApiRes Static Methods

• ok(result, message): Returns a success response (HTTP 200).
• created(result, message): Returns a resource creation response (HTTP 201).
• paginated(data, meta, message): Returns a success response (HTTP 200).

ApiRes.toJson(res: Response): void Method:

Send HTTP json Response.

new ApiRes({}, 'Hello World').toJson(res);

HttpError ❌

The HttpError class standardizes error handling by extending the native Error class. It’s used to throw HTTP-related errors, which are then caught by the globalErrorHandler middleware.

Usage:

import {HttpError, HttpStatus} from 'exutile';

// Example without async-handler
app.get('*', () => {
  new HttpError('Not Found', HttpStatus.NOT_FOUND).toJson(res); // Throw a 404 error
});

// Example with async-handler
app.post(
  '/example',
  handler(req => {
    if (!req.body.name) throw new BadRequestError('Name is required');
  }),
);

HttpError(msg, status, details):

• msg: This parameter accepts an error message, which can be a single string or an array of strings (required).
• status: The status code of the error, mirroring statusCode for general compatibility (default is 500).
• detail: This is an optional plain object that contains additional information about the error.

const err = new HttpError('Validation error.', 400, {
  username: 'Username is required',
  password: 'Password is required',
});

Note: If only a status code is provided, the HttpError class will automatically generate an appropriate error name based on that status code.

Common HTTP Errors:

• BadRequestError
• UnAuthorizedError
• NotFoundError
• ConflictError
• ForbiddenError
• PaymentRequiredError
• NotImplementedError
• InternalServerError

isHttpError(value) Static Method:

The HttpError.isHttpError(value) method determines if a specific value is an instance of the HttpError class.

// If it is an HttpError, send a JSON response with the error details
if (HttpError.isHttpError(err)) return err.toJson(res);
else
  // If it's not an HttpError, pass it to the next middleware for further handling
  next(err);

Error Properties:

• status: The HTTP status code associated with the error.
• message: A brief description of the error.
• stack: The stack trace of the error (available in development mode).
• details: Optional additional information about the error.

Custom ErrorHandler Middleware

export const errorHandler: ErrorRequestHandler = (err, req, res, next): any => {
  // Handle known HttpError instances
  if (HttpError.isHttpError(err)) return err.toJson(res);
  // Log unknown errors
  console.error(err);
  // Create an InternalServerError for unknown errors
  return new InternalServerError(
    config.dev ? err.message : 'Something went wrong',
    config.dev ? err.stack : null,
  ).toJson(res);
};

error.toJson(res: Response): void Method:

Send HTTP json Response.

new HttpError('Hello World').toJson(res);

error.getBody(): HttpErrorBody Method:

Converts an HttpError instance into a structured JSON format.

const body = new HttpError('Hello World').getBody();

HttpStatus ✅

The HttpStatus provides readable constants for standard HTTP status codes (2xx, 3xx, 4xx, 5xx) and Names, improving code clarity and consistency.

Usage:

import {HttpStatus} from 'exutile';

// Example: Basic usage in a route
app.get('/status-example', (req, res) => {
  res.status(HttpStatus.OK).json({message: 'All good!'});
});

// Example: Custom error handling middleware
app.use((req, res) => {
  res.status(HttpStatus.NOT_FOUND).json({
    error: 'Resource not found',
  });
});

// Example: Response with a 201 Created status
app.post('/create', (req, res) => {
  const resource = createResource(req.body);
  res.status(HttpStatus.CREATED).json({
    message: 'Resource created successfully',
    data: resource,
  });
});

HttpStatus.NAMES of HTTP Status Code Name:

The NAMES object provides a simple lookup for the descriptive names of HTTP status codes.

const statusName = HttpStatus.NAMES.$200; // 'OK'

Commonly Used HTTP Status Codes:

• 2xx: Success

  • HttpStatus.OK: 200 — Request succeeded.
  • HttpStatus.CREATED: 201 — Resource created.
  • HttpStatus.ACCEPTED: 202 — Request accepted for processing.
  • HttpStatus.NO_CONTENT: 204 — No content to send.
  • and more ....

• 3xx: Redirection

  • HttpStatus.MOVED_PERMANENTLY: 301 — Resource moved permanently.
  • HttpStatus.FOUND: 302 — Resource found at another URI.
  • HttpStatus.NOT_MODIFIED: 304 — Resource not modified.
  • and more ....

• 4xx: Client Error

  • HttpStatus.BAD_REQUEST: 400 — Bad request.
  • HttpStatus.UNAUTHORIZED: 401 — Authentication required.
  • HttpStatus.FORBIDDEN: 403 — Access forbidden.
  • HttpStatus.NOT_FOUND: 404 — Resource not found.
  • and more ....

• 5xx: Server Error

  • HttpStatus.INTERNAL_SERVER_ERROR: 500 — Internal server error.
  • HttpStatus.NOT_IMPLEMENTED: 501 — Not implemented.
  • HttpStatus.SERVICE_UNAVAILABLE: 503 — Service unavailable.
  • and more ....

Permission makePermission function

Generates a permission object mapping subjects and actions to permission strings.

/** Server Permissions */
const Permissions = makePermission({
  actions: ['create', 'read', 'update', 'delete'] as const,
  subjects: ['user', 'blog', 'comment'] as const,
  filter: {
    user: ['read'], // user only map read
  },
});

console.log(Permission.USER_READ); // user:read

proxyWrapper: Class Controllers 🏗️

exutile provides the utility proxyWrapper to make simplify working with class-based controllers in Express.

Usage:

// example-controller.ts
import {Request} from 'express';

// Controller Class
class ExampleController {
  constructor(private message: string) {}

  async getData(req: Request) {
    // Your logic here
    return ApiRes.ok({}, this.message);
  }
}

// example-routes.ts
import {Router} from 'express';
import {proxyWrapper} from 'exutile';
import {ExampleController} from './example-controller.ts';

const exampleRoutes = (): Router => {
  const router = Router();

  // Create a proxied instance of ExampleController
  const example = proxyWrapper(ExampleController, 'Hello World');

  // Configure routes
  return router.post('/data', example.getData);
};

proxyWrapper(clsOrInstance, ...args):

• Parameters:
  • clsOrInstance: A class constructor or an instance of a class.
  • args: Arguments for the class constructor (if clsOrInstance is a constructor).
• Returns: A proxied instance where all methods are wrapped with async-handler.

How It Works

• Instantiates the specified class if a constructor is provided.
• Wraps all its methods with async-handler, allowing for automatic handling of asynchronous operations.
• Prevents method/property overrides for safety.

Using Dependency Injection Libraries:

You can use proxyWrapper with dependency injection libraries like tsyringe or typedi.

Example with tsyringe

const exampleRoutes = (): Router => {
  const router = Router();

  // Create a proxied instance of ExampleController
  const example = proxyWrapper(container.resolve(ExampleController));

  // Configure routes
  return router.post('/data', example.getData);
};

Example with typedi

const exampleRoutes = (): Router => {
  const router = Router();

  // Create a proxied instance of ExampleController
  const example = proxyWrapper(Container.get(ExampleController));

  // Configure routes
  return router.post('/data', example.getData);
};

Conclusion 🏁

exutile is a powerful tool designed to simplify and enhance Express.js applications by providing essential features out of the box. Whether you’re building a simple API or a complex web application, exutile helps you maintain clean and manageable code.

Contributing 🤝

Contributions are highly appreciated! To contribute:

1. Fork the repository.
2. Create a new branch for your feature or bug fix.
3. Submit a pull request with a clear description of your changes.

Author 👤

• Created by Aashish Panchal.
• GitHub: @aashishpanchal

License 📜

MIT © Aashish Panchal