What is a joi?

"Joi" most commonly refers to Joi, a JavaScript schema description language and validator. It's used to define the structure and data types of objects, and then validate whether incoming data conforms to those specifications. This is particularly useful for:

• Data validation in APIs: Ensuring that requests and responses adhere to a pre-defined format.
• Input sanitization: Cleaning and transforming data before it's used in your application, preventing vulnerabilities.
• Data modelling: Defining the structure of your data clearly and consistently.

Key features of Joi include:

• Schema definition: You use a fluent, object-oriented API to create schemas that specify data types (string, number, boolean, array, object, etc.), required fields, allowed values, and more.
• Validation: Joi provides functions to easily validate data against your schemas, returning errors if the data doesn't match. These errors are often detailed and helpful for debugging.
• Extensibility: You can extend Joi's functionality by creating custom validation rules.
• Asynchronous validation: Supports asynchronous validation for scenarios involving database lookups or other external operations.

Joi is a popular choice due to its flexibility, ease of use, and comprehensive error reporting. It helps to improve code quality, security, and maintainability by ensuring data integrity throughout your application.

There are other less common meanings of "joi," but in most technical contexts, this is the one intended.