In a REST API context, validation can be applied at various levels. At the request level, input data can be validated using middleware functions before it reaches the controller. This ensures that only valid and expected data is processed further.
For instance, in Express.js, you could use libraries like ‘express-validator’ or ‘joi’. These allow for checking of required fields, type matching, range constraints, and custom validation rules.
At the database level, schemas can enforce certain validations. For example, MongoDB’s Mongoose library allows defining schema-based validation on fields such as string length, numerical min/max values, or even regex patterns.
Additionally, HTTP status codes can communicate validation errors to clients. A 400 Bad Request indicates client-side issues, while a 422 Unprocessable Entity suggests validation problems.
