Formv

Formv is a software library designed to manage and validate user input across web applications. It provides a framework-agnostic approach to describing forms, validating data, and normalizing values from client-side and server-side sources.

A formv form is defined by a schema that describes fields, their data types, constraints, and transformation rules. Each field can specify required, min/max length, numeric ranges, pattern matching, and custom validators. Transformations allow trimming, case conversion, or type coercion before validation. Validation rules can be synchronous or asynchronous, enabling checks like server-side uniqueness.

Under the hood, formv compiles a form schema into a validation function and uses adapters to integrate with UI frameworks; it includes a plugin system for localization, error messaging, and accessibility features. Server-side validation mirrors client-side rules to ensure consistent data quality.

Formv originated as a lightweight solution to unify client and server form processing. It is designed to be interoperable with existing standards such as JSON Schema and popular validation libraries, and it emphasizes clear error reporting and predictable behavior.

See also: JSON Schema, Yup, Formik, AJV.