Building Enterprise JavaScript Applications

Expressiveness

JSON Schema supports many validation keywords and data formats, as defined in the IETF memo JSON Schema Validation: A Vocabulary for Structural Validation of JSON (json-schema.org/latest/json-schema-validation.html); however, due to the restrictions of JSON itself, JSON Schema lacks the ability to define custom validation logic in the form of functions.

For example, JSON Schema does not provide a way to express the following logic: "if the age property is below 18, then the hasParentalConsent property must be set to true." Thus, if you want to perform more complicated checks, these must be done as a separate function in JavaScript. Alternatively, some JSON Schema-based validation libraries extend the JSON Schema syntax and ...