Common Utilities for Express Applications

A collection of reusable utilities and middleware for Express.js applications, aimed at handling common tasks such as error handling, user authentication, and request validation.

Table of Contents

• Installation
• Usage
  • Error Handling Middleware
  • Current User Middleware
  • Request Validation Middleware
• Custom Errors
  • CustomError
  • DatabaseConnectionError
  • RequestValidationError
• Contributing
• License

Installation

Install the package via npm:

npm install @sandeshghoti/tickets-commonutils

Usage

Error Handling Middleware

This middleware is used to handle errors thrown during request processing. It catches custom errors and responds with appropriate HTTP status codes and messages.

Example

import express from "express";
import { errorHandler } from "@sandeshghoti/tickets-commonutils";
import { CustomError } from "@sandeshghoti/tickets-commonutils/errors";

const app = express();

// Middleware to handle errors
app.use(errorHandler);

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

Current User Middleware

This middleware attaches the current user to the request object if a valid JWT token is present in the session. It decodes the JWT token and attaches the user payload to req.user.

Example

import express from "express";
import { currentUser } from "@sandeshghoti/tickets-commonutils";

const app = express();

// Middleware to attach current user
app.use(currentUser);

app.get("/profile", (req, res) => {
  if (req.user) {
    res.send(`Hello, ${req.user.email}`);
  } else {
    res.send("Hello, Guest");
  }
});

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

Request Validation Middleware

This middleware validates incoming requests based on the validation rules defined using express-validator. It throws a RequestValidationError if the validation fails.

Example

import express from "express";
import { body } from "express-validator";
import { validateRequest } from "@sandeshghoti/tickets-commonutils";

const app = express();
app.use(express.json());

app.post(
  "/signup",
  [
    body("email").isEmail().withMessage("Email must be valid"),
    body("password")
      .isLength({ min: 6 })
      .withMessage("Password must be at least 6 characters"),
    validateRequest,
  ],
  (req, res) => {
    res.send("User signed up successfully");
  }
);

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

Custom Errors

CustomError

An abstract class for defining custom errors with specific HTTP status codes and error messages.

Example

import { CustomError } from "@sandeshghoti/tickets-commonutils/errors";

class NotFoundError extends CustomError {
  statusCode = 404;

  constructor() {
    super("Resource not found");
    Object.setPrototypeOf(this, NotFoundError.prototype);
  }

  serializeErrors() {
    return [{ message: "Resource not found" }];
  }
}

DatabaseConnectionError

An error thrown when there is an issue connecting to the database. Extends CustomError.

Example

import { DatabaseConnectionError } from "@sandeshghoti/tickets-commonutils/errors";

app.get("/connect", (req, res) => {
  try {
    // Simulate database connection
    throw new DatabaseConnectionError();
  } catch (err) {
    next(err);
  }
});

RequestValidationError

An error thrown when request validation fails. Extends CustomError and provides details about the validation errors.

Example

import { body } from "express-validator";
import { RequestValidationError } from "@sandeshghoti/tickets-commonutils/errors";

app.post(
  "/login",
  [
    body("email").isEmail().withMessage("Email must be valid"),
    body("password").notEmpty().withMessage("Password is required"),
    (req, res, next) => {
      const errors = validationResult(req);
      if (!errors.isEmpty()) {
        throw new RequestValidationError(errors.array());
      }
      next();
    },
  ],
  (req, res) => {
    res.send("User logged in successfully");
  }
);

Contributing

Contributions are welcome! Please feel free to submit a pull request or open an issue if you find any bugs or have suggestions for improvements.

License

This package is open source and available under the MIT License.