Function getEditableChildAndIndex

packages/editor/src/utils/dom.ts:58–96

(
  parent: DOMElement,
  index: number,
  direction: 'forward' | 'backward',
)

 */

export const getEditableChildAndIndex = (
  parent: DOMElement,
  index: number,
  direction: 'forward' | 'backward',
): [DOMNode, number] => {
  const { childNodes } = parent
  let child = childNodes[index]
  let i = index
  let triedForward = false
  let triedBackward = false

  // While the child is a comment node, or an element node with no children,
  // keep iterating to find a sibling non-void, non-comment node.
  while (isDOMComment(child) || (isDOMElement(child) && child.childNodes.length === 0)) {
    if (triedForward && triedBackward) {
      break
    }

    if (i >= childNodes.length) {
      triedForward = true
      i = index - 1
      direction = 'backward'
      continue
    }

    if (i < 0) {
      triedBackward = true
      i = index + 1
      direction = 'forward'
      continue
    }

    child = childNodes[i]
    index = i
    i += direction === 'forward' ? 1 : -1
  }

  return [child, index]
}

/**
 * Get the nearest editable child at `index` in a `parent`, preferring