Function isValidArrayIndex

packages/core/src/document/prop/prop.ts:735–738

(key: any, limit = -1)

 * check if the key is a valid array index
 */
export function isValidArrayIndex(key: any, limit = -1): key is number {
  const n = Number.parseFloat(String(key))
  return n >= 0 && Math.floor(n) === n && Number.isFinite(n) && (limit < 0 || n < limit)
}