Express Dynamic Middlewares

This npm package acts as a data security guard for your Express applications. It offers validation for incoming data (emails, usernames, etc.) and provides custom error handling. Additionally, it includes middleware wrapping functions to streamline asynchronous operations and enhance your development experience.

Installation

Install the package using npm or yarn:

npm install express-dynamic-middlewares

or

yarn add express-dynamic-middlewares

Usage/Examples

ErrorHandler Class
The ErrorHandler class is a custom error class that extends the native JavaScript Error class. It allows you to specify a statusCode and message for the error.

throw new ErrorHandler(404, "Page not found");

errorHandler Middleware
The errorHandler middleware handles errors thrown in your Express application, providing a standardized JSON response.
Catches all errors thrown in your application routes and returns a JSON response with:

• success: false to indicate an error
• error: message containing the error message or a default "Internal server error"
• Optional statusCode for specific error classification (defaults to 500)
• Make sure to use this middleware after all routes

app.use(errorHandler);

asyncHandler Middleware
The asyncHandler middleware wraps asynchronous functions to catch errors and pass them to the next middleware. This helps in keeping your route handlers clean and free from try-catch blocks. It takes two arguments one is function and second is Array to handle specific errors. Array is optional argument.

app.get("/get", asyncHandler(getFunction));

Optional Error Handling Array: Customize error handling by providing an optional array as the second argument to asyncHandler. This array lets you define specific error types and their corresponding HTTP status codes and messages.

const errorOptions = [
    {
        type: TypeError,
        statusCode: 400,
        message: "Bad request due to type error",
    },
];

app.get("/data", asyncHandler(getData, errorOptions)); // getData is your asynchronous function

validator Middleware
The validator function creates a middleware for validating parameters in request body.

app.post(
    "/register",
    validator(
        "username", //Make sure that request body contain username
        true, // (true means check for emptiness or existence)(Optional)(Default : true)
        false, // (false means don't check for whether it's an email or not)(Optional)(Default : false)
        5, // Minimum length(Optional)(Default : 0)(When 0 don't check for minLenght)
        20, // Maximum length(Optional)(Default : 0)(When 0 don't check for maxLength)
        false // (false means don't check for whether it's phone no. or not)(Optional)(Default : false)
    ),
    asyncHandler(registerUser)
);

Additional Validation Middlewares: For your convenience, express-dynamic-middlewares offers pre-built validation middlewares like validateString, validateNumber, and validateBoolean.

app.get(
    "/get",
    validateString("name"),
    validator("name", true, false, 5, 20, false),
    asyncHandler(getFunction)
);

Example

const express = require("express");
const {
    ErrorHandler,
    errorHandler,
    asyncHandler,
    validator,
} = require("express-dynamic-middlewares");

const app = express();

//All routes
app.post(
    "/register",
    validator("email", true, true, 0, 0, false),
    asyncHandler(async (req, res) => {
        //Throw error
        if (username === "[e-mail]") {
            throw new ErrorHandler(
                403,
                "This email is not allowed for registration."
            );
        }
        res.json({ success: true, message: "User registered successfully!" });
    })
);

app.use(errorHandler);

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

Handling Custom Errors

To handle specific error types, you can customize one array. This array should contain objects with type, statusCode, and message properties. Add this logic inside your project where asyncHandler is used.

const express = require("express");
const {
    ErrorHandler,
    errorHandler,
    asyncHandler,
} = require("express-dynamic-middlewares");

const app = express();

const errorTypes = [
    {
        type: TypeError,
        statusCode: 400,
        message: "Type error occurred",
    },
    {
        type: ReferenceError,
        statusCode: 500,
        message: "Reference error occurred",
    },
    {
        type: CastError,
        statusCode: 400,
        message: "Cast error occurred",
    },
];

const getFunction = asyncHandler(async (req, res) => {
    //function...
}, errorOptions); //Pass error options to handle perticular errors

//All routes
app.get("/data", getFunction);

app.use(errorHandler);

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

License

MIT

Authors

@Dev Patel