/react

name: react
description: React renderer for json-render that turns JSON specs into React components. Use when working with @json-render/react, building React UIs from JSON, creating component catalogs, or rendering AI-generated specs.

@json-render/react

React renderer that converts JSON specs into React component trees.

Quick Start

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

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

function App({ spec }) {
  return <Renderer spec={spec} registry={registry} />;
}

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 }) => (
      <button className={props.variant}>{props.label}</button>
    ),
    Card: ({ props, children }) => (
      <div className="card">
        <h2>{props.title}</h2>
        {children}
      </div>
    ),
  },
});

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 });

<StateProvider store={store}>{children}</StateProvider>

// 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`:

<JSONUIProvider
  functions={{ fullName: (args) => `${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 }) => (
  <button onClick={() => emit("press")}>{props.label}</button>
),

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

{
  "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/co