Package Exports

This package does not declare an exports field, so the exports above have been automatically detected and optimized by JSPM instead. If any package subpath is missing, it is recommended to post an issue to the original package (@chakra-ui/descendant) to support the "exports" field. If that is not possible, create a JSPM override to customize the exports field for this package.

Readme

Descendant

Keep track of descendant components and their relative indices.

A descendant index solution for better accessibility support in compound components.

Note 🚨: This package is primarily intended for internal use by the Chakra UI library. You should not use it directly in your production projects.

Installation

yarn add @chakra-ui/descendant

# or

npm i @chakra-ui/descendant

Motivation

Descendants observer is a utility hook for keeping track of descendant elements and their relative indices.

In short, this package allows each item in a list to know its relative index and the parent of the list can keep track of each child, without needing to render in a loop and pass each component an index.

This enables component composition:

<List>
  <Item /> // I'm index 0
  <Item /> // I'm index 1<div>
    <div>
      <Item /> // I'm arbitrarily nested, but still know that I'm index 2
    </div>
  </div>
</List>

Usage

import { createDescendantContext } from "@chakra-ui/descendant"
import * as React from "react"

const [
  DescendantsProvider,
  useDescendantsContext,
  useDescendants,
  useDescendant,
] = createDescendantContext()

const MenuContext = React.createContext({})

function Menu({ children }) {
  // 1. Call the `useDescendants` hook
  const descendants = useDescendants()

  const [selected, setSelected] = React.useState(1)
  const context = React.useMemo(() => ({ selected, setSelected }), [selected])

  return (
    // 2. Add the descendants context
    <DescendantsProvider value={descendants}>
      <MenuContext.Provider value={context}>
        <div role="menu" style={{ maxWidth: 320 }}>
          <button
            onClick={() => {
              const prev = descendants.prev(selected)
              prev.node.focus()
              setSelected(prev.index)
            }}
          >
            Prev
          </button>
          <button
            onClick={() => {
              const next = descendants.next(selected)
              next.node.focus()
              setSelected(next.index)
            }}
          >
            Next
          </button>
          {children}
        </div>
      </MenuContext.Provider>
    </DescendantsProvider>
  )
}

const MenuItem = ({ children }) => {
  const { selected, setSelected } = React.useContext(MenuContext)

  // 3. Read from descendant context
  const { index, register } = useDescendant()

  const isSelected = index === selected

  return (
    <div
      role="menuitem"
      ref={register}
      aria-selected={isSelected}
      onMouseMove={() => setSelected(index)}
      style={{ color: isSelected ? "red" : "black" }}
    >
      {children} - {index}
    </div>
  )
}

const Example = () => {
  const [show, setShow] = React.useState(false)
  const [show2, setShow2] = React.useState(false)

  const toggle = () => {
    setShow(!show)
    if (!show === true) {
      setTimeout(() => {
        setShow2(true)
      }, 1000)
    }
  }

  return (
    <div>
      <button onClick={toggle}>Toggle</button>
      <Menu>
        <MenuItem>One</MenuItem>
        {show && <MenuItem>Two</MenuItem>}
        <MenuItem>Three</MenuItem>
        <MenuItem>Four</MenuItem>
        <div>
          {show2 && <MenuItem>Testing 🌟</MenuItem>}
          <MenuItem>Five</MenuItem>
        </div>
      </Menu>
    </div>
  )
}