Yup express middleware

Offers Yup schema validation for Express with first class typescript support.

npm i yup-express-middleware

or

yarn add yup-express-middleware

Features

1. req.body and/or req.query can be validated
2. Yup transformations supported
3. req.body and/or req.query will be of the type of your schema in your controller!
4. No messy try-catch validation handling in your controllers, this library will automatically call express' error route handler (optionally with a custom error you can define).

Usage

import { validation } from "yup-express-middleware";
import * as yup from "yup";
import express from "express";

const app = express();

const schema = yup.object().shape({
    name: yup.string().required(),
    age: yup
        .number()
        .required()
        .transform(val => val + 2),
});

const schema2 = yup.object({ bla: yup.object({ bloo: yup.string() }) });

app.post("/", validation({ body: schema, query: schema2 }), (req, res, next) => {
    const { name, age } = req.body;
    //  string^   ^number => validated, transformed (if the schema did so) and typed correctly

    const {
        bla: { bloo }, // bloo is typed correctly as string
    } = req.query;
});

When validation fails

class HttpError extends Error {
    constructor(message: string, public status: number) {
        super(message);
    }
}

class BadRequestError extends HttpError {
    constructor(message: string) {
        super(message, 400);
    }
}

app.post(
    "/",
    validation(
        { body: schema },
        { yupOptions: { abortEarly: false }, ErrorClass: BadRequestError }
    ),
    (req, res, next) => {
        // If validation fails, this won't get called
        // the middleware will call `next(new BadRequestError("the message provided by yup"))`
        // and you will have to catch that in your express error handler.
    }
);

// for example

app.use(((err, req, res, next) => {
    if (res.headersSent) next(err);
    if (err.name === "BadRequestError") {
        res.status(err.status).json({
            reason: "Validation Error",
            error: err.message,
        });
    }
}) as ErrorRequestHandler);

API

validation(schema, options);

schema:
    body: (optional) yup schema
    query: (optional) yup schema

options:

    yupOptions: Options to pass to yup.validate()

    ErrorClass: The error class to throw when validation fails (defaults to `Error`)

    finallyFunction: the function to call regardless of whether validation succeeds or fails)