ESC JSON Form Core

ESC JSON Form Core: The Engine Behind Schema-Driven Forms

Building a form editor for arbitrary JSON data usually means reimplementing the same plumbing over and over -- tracking nested state, validating fields, and reacting to changes -- once per UI framework. ESC JSON Form Core exists to solve that problem exactly once: it's a pure TypeScript library with no UI framework dependency at all, designed to sit underneath framework-specific renderers like esc-json-form-react and esc-json-form-angular.

At the center of the library is a store pattern. Calling createJsonFormStore(initialValue, schema?) returns a store with typed getters and setters, path-based access for deeply nested fields, array helpers for dynamic list editing, built-in validation, and a subscriber model for reactive updates.

Why ESC JSON Form Core Stands Out

• Framework-agnostic -- pure TypeScript with zero UI dependencies. Use it headless, or as the foundation for a custom adapter in any framework.
• Store pattern -- getValue, setValue, getAtPath, setAtPath, setTypeAtPath, and a subscribe listener give you full control over form state.
• Array helpers -- addArrayItem and removeArrayItem manage dynamic array fields at any path depth without manual index bookkeeping.
• Schema validation -- define rules like required, minLength, min, and type directly in a schema, then call validate() for typed error results.
• Typed form tree -- getTree() returns a nested tree that mirrors the JSON structure, which adapter packages use to drive rendering without reimplementing schema traversal.
• Reactive subscriptions -- store.subscribe(listener) fires on any value change, so it plugs into any reactive framework or plain JavaScript.

ESC JSON Form Core can also be used directly for headless form logic, server-side validation, or as the basis for adapters targeting frameworks beyond React and Angular. It's free, open source, and published to npm as esc-json-form-core.