Express Middleware for Request Validation and Transformation

dat-middleware is an Express.js middleware library that provides a fluent and declarative API for common request data operations. It focuses on validating and transforming `req.body`, `req.query`, and `req.params` against various criteria such as required fields, data types (string, number, array, boolean, object, function), specific class instances (`instanceOf`), and regular expressions (`matches`). Developers can also integrate custom validation logic using the `validate()` method. Upon validation failure, the middleware automatically calls `next()` with a 400 Bad Request error object generated by `spumko/boom`, simplifying error handling. The current stable version is 1.10.4. Given its last update several years ago, it operates primarily in a maintenance mode, offering a stable but not actively developed solution for Express input validation. Its key differentiator is the chaining syntax for defining validation rules directly within the middleware stack.