Joi
Joi is a powerful schema description language and data validator for JavaScript and TypeScript, primarily used in Node.js applications. It allows developers to define the structure and constraints of data (like objects, strings, numbers) and validate input against those schemas, ensuring data integrity and security. It is commonly integrated with web frameworks like Express.js to validate request payloads, query parameters, and headers.
Developers should learn Joi when building Node.js applications that require robust input validation, such as REST APIs, to prevent malformed or malicious data from causing errors or security vulnerabilities. It is particularly useful in scenarios like user registration forms, API endpoints, and configuration management, where validating data types, ranges, and formats (e.g., emails, passwords) is critical for reliability and compliance with business rules.