its-fine

A collection of escape hatches for React.

As such, you can go beyond React's component abstraction; components are self-aware and can tap into the React Fiber tree. This enables powerful abstractions that can modify or extend React behavior without explicitly taking reconciliation into your own hands.

Table of Contents

• Components
  • FiberProvider
• Hooks
  • useFiber
  • useContainer
  • useNearestChild
  • useNearestParent
  • useContextMap
  • useContextBridge
• Utils
  • traverseFiber

Components

FiberProvider

A react-internal Fiber provider. This component binds React children to the React Fiber tree. Call its-fine hooks within this.

Note: pmndrs renderers like react-three-fiber implement this internally to make use of useContextBridge, so you would only need this when using hooks inside of react-dom or react-native.

import * as ReactDOM from 'react-dom/client'
import { FiberProvider, useFiber } from 'its-fine'

function App() {
  const fiber = useFiber()
}

ReactDOM.createRoot(document.getElementById('root')!).render(
  <FiberProvider>
    <App />
  </FiberProvider>,
)

Hooks

Useful React hook abstractions for manipulating and querying from a component. These must be called within a FiberProvider component.

useFiber

Returns the current react-internal Fiber. This is an implementation detail of react-reconciler.

import * as React from 'react'
import { type Fiber, useFiber } from 'its-fine'

function Component() {
  // Returns the current component's react-internal Fiber
  const fiber: Fiber<null> | undefined = useFiber()

  // function Component() {}
  if (fiber) console.log(fiber.type)
}

useContainer

Returns the current react-reconciler container info passed to Reconciler.createContainer.

In react-dom, a container will point to the root DOM element; in react-three-fiber, it will point to the root Zustand store.

import * as React from 'react'
import { useContainer } from 'its-fine'

function Component() {
  // Returns the current renderer's root container
  const container: HTMLDivElement | undefined = useContainer<HTMLDivElement>()

  // <div> (e.g. react-dom)
  if (container) console.log(container)
}

useNearestChild

Returns the nearest react-reconciler child instance or the node created from Reconciler.createInstance.

In react-dom, this would be a DOM element; in react-three-fiber this would be an Instance descriptor.

import * as React from 'react'
import { useNearestChild } from 'its-fine'

function Component() {
  // Returns a React Ref which points to the nearest child <div /> element.
  // Omit the element type to match the nearest element of any kind
  const childRef: React.MutableRefObject<HTMLDivElement | undefined> = useNearestChild<HTMLDivElement>('div')

  // Access child Ref on mount
  React.useEffect(() => {
    // <div> (e.g. react-dom)
    const child = childRef.current
    if (child) console.log(child)
  }, [])

  // A child element, can live deep down another component
  return <div />
}

useNearestParent

Returns the nearest react-reconciler parent instance or the node created from Reconciler.createInstance.

In react-dom, this would be a DOM element; in react-three-fiber this would be an instance descriptor.

import * as React from 'react'
import { useNearestParent } from 'its-fine'

function Component() {
  // Returns a React Ref which points to the nearest parent <div /> element.
  // Omit the element type to match the nearest element of any kind
  const parentRef: React.MutableRefObject<HTMLDivElement | undefined> = useNearestParent<HTMLDivElement>('div')

  // Access parent Ref on mount
  React.useEffect(() => {
    // <div> (e.g. react-dom)
    const parent = parentRef.current
    if (parent) console.log(parent)
  }, [])
}

// A parent element wrapping Component, can live deep up another component
;<div>
  <Component />
</div>

useContextMap

Returns a map of all contexts and their values.

import * as React from 'react'
import { useContextMap } from 'its-fine'

const SomeContext = React.createContext<string>(null!)

function Component() {
  const contextMap = useContextMap()
  return contextMap.get(SomeContext)
}

useContextBridge

React Context currently cannot be shared across React renderers but explicitly forwarded between providers (see react#17275). This hook returns a ContextBridge of live context providers to pierce Context across renderers.

Pass ContextBridge as a component to a secondary renderer to enable context-sharing within its children.

import * as React from 'react'
// react-nil is a secondary renderer that is usually used for testing.
// This also includes Fabric, react-three-fiber, etc
import * as ReactNil from 'react-nil'
// react-dom is a primary renderer that works on top of a secondary renderer.
// This also includes react-native, react-pixi, etc.
import * as ReactDOM from 'react-dom/client'
import { type ContextBridge, useContextBridge, FiberProvider } from 'its-fine'

function Canvas(props: { children: React.ReactNode }) {
  // Returns a bridged context provider that forwards context
  const Bridge: ContextBridge = useContextBridge()
  // Renders children with bridged context into a secondary renderer
  ReactNil.render(<Bridge>{props.children}</Bridge>)
}

// A React Context whose provider lives in react-dom
const DOMContext = React.createContext<string>(null!)

// A component that reads from DOMContext
function Component() {
  // "Hello from react-dom"
  console.log(React.useContext(DOMContext))
}

// Renders into a primary renderer like react-dom or react-native,
// DOMContext wraps Canvas and is bridged into Component
ReactDOM.createRoot(document.getElementById('root')!).render(
  <FiberProvider>
    <DOMContext.Provider value="Hello from react-dom">
      <Canvas>
        <Component />
      </Canvas>
    </DOMContext.Provider>
  </FiberProvider>,
)

Utils

Additional exported utility functions for raw handling of Fibers.

traverseFiber

Traverses up or down a Fiber, return true to stop and select a node.

import { type Fiber, traverseFiber } from 'its-fine'

// Traverses through the Fiber tree, returns the current node when `true` is passed via selector
const parentDiv: Fiber<HTMLDivElement> | undefined = traverseFiber<HTMLDivElement>(
  // Input Fiber to traverse
  fiber as Fiber,
  // Whether to ascend and walk up the tree. Will walk down if `false`
  true,
  // A Fiber node selector, returns the first match when `true` is passed
  (node: Fiber<HTMLDivElement | null>) => node.type === 'div',
)