react

by vercel

Convert JSON specs into React component trees with type-safe props and state management. Define catalogs with Zod schemas for component props, then implement components with automatic type safety and validation Built-in state management via StateProvider with two-way binding ( $bindState ), conditional rendering, and external store integration (Redux, Zustand, XState) Event system with action dispatching, state watchers, and four built-in actions (setState, pushState, removeState,... npx skills add https://github.com/vercel-labs/json-render --skill react Download ZIPGitHub15.6k

@json-render/react

React renderer that converts JSON specs into React component trees.

Creating a Catalog

import { defineCatalog } from "@json-render/core";
import { schema } from "@json-render/react/schema";
import { defineRegistry } from "@json-render/react";
import { z } from "zod";

// Create catalog with props schemas
export const catalog = defineCatalog(schema, {
 components: {
 Button: {
 props: z.object({
 label: z.string(),
 variant: z.enum(["primary", "secondary"]).nullable(),
 }),
 description: "Clickable button",
 },
 Card: {
 props: z.object({ title: z.string() }),
 description: "Card container with title",
 },
 },
});

// Define component implementations with type-safe props
const { registry } = defineRegistry(catalog, {
 components: {
 Button: ({ props }) => (
 {props.label} 
 ),
 Card: ({ props, children }) => (

## {props.title}

{children}
 

 ),
 },
});

Spec Structure (Element Tree)

The React schema uses an element tree format:

{
 "root": {
 "type": "Card",
 "props": { "title": "Hello" },
 "children": [
 { "type": "Button", "props": { "label": "Click me" } }
 ]
 }
}

Visibility Conditions

Use visible on elements to show/hide based on state. New syntax: { "$state": "/path" }, { "$state": "/path", "eq": value }, { "$state": "/path", "not": true }, { "$and": [cond1, cond2] } for AND, { "$or": [cond1, cond2] } for OR. Helpers: visibility.when("/path"), visibility.unless("/path"), visibility.eq("/path", val), visibility.and(cond1, cond2), visibility.or(cond1, cond2).

Providers

Provider Purpose StateProvider Share state across components (JSON Pointer paths). Accepts optional store prop for controlled mode. ActionProvider Handle actions dispatched via the event system VisibilityProvider Enable conditional rendering based on state ValidationProvider Form field validation

External Store (Controlled Mode)

Pass a StateStore to StateProvider (or JSONUIProvider / createRenderer) to use external state management (Redux, Zustand, XState, etc.):

import { createStateStore, type StateStore } from "@json-render/react";

const store = createStateStore({ count: 0 });

 {children} 

// Mutate from anywhere — React re-renders automatically:
store.set("/count", 1);

When store is provided, initialState and onStateChange are ignored.

Dynamic Prop Expressions

Any prop value can be a data-driven expression resolved by the renderer before components receive props:

• { "$state": "/state/key" } - reads from state model (one-way read)

• { "$bindState": "/path" } - two-way binding: reads from state and enables write-back. Use on the natural value prop (value, checked, pressed, etc.) of form components.

• { "$bindItem": "field" } - two-way binding to a repeat item field. Use inside repeat scopes.

• Filtered lists: repeat plus an $item visible condition on the same container renders only matching items: { "repeat": { "statePath": "/tasks", "key": "id" }, "visible": { "$item": "status", "eq": "todo" }, "children": ["task-card"] }. AND-composed $state conjuncts gate the container shell; $item/$index conjuncts filter items.

• { "$cond": <condition>, "$then": <value>, "$else": <value> } - conditional value

• { "$template": "Hello, ${/name}!" } - interpolates state values into strings

• { "$computed": "fn", "args": { ... } } - calls registered functions with resolved args

{
 "type": "Input",
 "props": {
 "value": { "$bindState": "/form/email" },
 "placeholder": "Email"
 }
}

Components do not use a statePath prop for two-way binding. Use { "$bindState": "/path" } on the natural value prop instead.

Components receive already-resolved props. For two-way bound props, use the useBoundProp hook with the bindings map the renderer provides.

Register $computed functions via the functions prop on JSONUIProvider or createRenderer:

 `${args.first} ${args.last}` }}
>

Event System

Components use emit to fire named events, or on() to get an event handle with metadata. The element's on field maps events to action bindings:

// Simple event firing
Button: ({ props, emit }) => (
 emit("press")}>{props.label} 
),

// Event handle with metadata (e.g. preventDefault)
Link: ({ props, on }) => {
 const click = on("click");
 return (
 {
 if (click.shouldPreventDefault) e.preventDefault();
 click.emit();
 }}>{props.label} 
 );
},

{
 "type": "Button",
 "props": { "label": "Submit" },
 "on": { "press": { "action": "submit" } }
}

The EventHandle returned by on() has: emit(), shouldPreventDefault (boolean), and bound (boolean).

State Watchers

Elements can declare a watch field (top-level, sibling of type/props/children) to trigger actions when state values change:

{
 "type": "Select",
 "props": { "value": { "$bindState": "/form/country" }, "options": ["US", "Canada"] },
 "watch": { "/form/country": { "action": "loadCities" } },
 "children": []
}

Built-in Actions

The setState, pushState, removeState, and validateForm actions are built into the React schema and handled automatically by ActionProvider. They are injected into AI prompts without needing to be declared in catalog actions:

{ "action": "setState", "params": { "statePath": "/activeTab", "value": "home" } }
{ "action": "pushState", "params": { "statePath": "/items", "value": { "text": "New" } } }
{ "action": "removeState", "params": { "statePath": "/items", "index": 0 } }
{ "action": "validateForm", "params": { "statePath": "/formResult" } }

validateForm validates all registered fields and writes { valid, errors } to state.

Note: statePath in action params (e.g. setState.statePath) targets the mutation path. Two-way binding in component props uses { "$bindState": "/path" } on the value prop, not statePath.

useBoundProp

For form components that need two-way binding, use useBoundProp with the bindings map the renderer provides when a prop uses { "$bindState": "/path" } or { "$bindItem": "field" }:

import { useBoundProp } from "@json-render/react";

Input: ({ element, bindings }) => {
 const [value, setValue] = useBoundProp (
 element.props.value,
 bindings?.value
 );
 return (
 setValue(e.target.value)}
 />
 );
},

useBoundProp(propValue, bindingPath) returns [value, setValue]. The value is the resolved prop; setValue writes back to the bound state path (no-op if not bound).

BaseComponentProps

For building reusable component libraries not tied to a specific catalog (e.g. @json-render/shadcn):

import type { BaseComponentProps } from "@json-render/react";

const Card = ({ props, children }: BaseComponentProps ) => (
 {props.title}{children}

);

defineRegistry

defineRegistry conditionally requires the actions field only when the catalog declares actions. Catalogs with actions: {} can omit it.

Key Exports

Export Purpose defineRegistry Create a type-safe component registry from a catalog Renderer Render a spec using a registry schema Element tree schema (includes built-in state actions: setState, pushState, removeState, validateForm) useStateStore Access state context useStateValue Get single value from state useBoundProp Two-way binding for $bindState/$bindItem expressions useActions Access actions context useAction Get a single action dispatch function useOptionalValidation Non-throwing variant of useValidation (returns null if no provider) useUIStream Stream specs from an API endpoint createStateStore Create a framework-agnostic in-memory StateStore StateStore Interface for plugging in external state management BaseComponentProps Catalog-agnostic base type for reusable component libraries EventHandle Event handle type (emit, shouldPreventDefault, bound) ComponentContext Typed component context (catalog-aware)

Quick Start

import { defineRegistry, Renderer } from "@json-render/react";
import { catalog } from "./catalog";

const { registry } = defineRegistry(catalog, {
 components: {
 Card: ({ props, children }) => {props.title}{children}
,
 },
});

function App({ spec }) {
 return ;
}