Json-render react

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.

install

source · Clone the upstream repo

git clone https://github.com/vercel-labs/json-render

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/vercel-labs/json-render "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/react" ~/.claude/skills/vercel-labs-json-render-react && rm -rf "$T"

manifest: skills/react/SKILL.md

source content

@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

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.

{ "$cond": <condition>, "$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.

$computed

functions via the

functions

prop on

JSONUIProvider

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/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" }

{ "$bindItem": "field" }

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

Input: ({ element, bindings }) => {
  const [value, setValue] = useBoundProp<string>(
    element.props.value,
    bindings?.value
  );
  return (
    <input
      value={value ?? ""}
      onChange={(e) => 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<{ title?: string }>) => (
  <div>{props.title}{children}</div>
);

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)