slate/packages/slate-react/src/hooks/use-selected.ts

import { useCallback } from 'react'
import { Editor, Range } from 'slate'
import { useElementIf } from './use-element'
import { useSlateSelector } from './use-slate-selector'
import { ReactEditor } from '../plugin/react-editor'

/**
 * Get the current `selected` state of an element.
 */

export const useSelected = (): boolean => {
  const element = useElementIf()

  // Breaking the rules of hooks is fine here since `!element` will remain true
  // or false for the entire lifetime of the component this hook is called from.
  // TODO: Decide if we want to throw an error instead when calling
  // `useSelected` outside of an element (potentially a breaking change).
  if (!element) return false

  // eslint-disable-next-line react-hooks/rules-of-hooks
  const selector = useCallback(
    (editor: Editor) => {
      if (!editor.selection) return false
      const path = ReactEditor.findPath(editor, element)
      const range = Editor.range(editor, path)
      return !!Range.intersection(range, editor.selection)
    },
    [element]
  )

  // eslint-disable-next-line react-hooks/rules-of-hooks
  return useSlateSelector(selector, undefined, {
    // Defer the selector until after `Editable` has rendered so that the path
    // will be accurate.
    deferred: true,
  })
}