Optional in nested Object

optional-in-object.js

function optional(obj: any, ...keys: string[]) {
  let opt = obj;
  while (keys.length && opt[keys[0]] !== undefined) {
    const key = keys.shift();
    opt = opt[key];
  }
  return keys.length ? false : opt;
}

const scrollHeight = optional(someDOMNode, "previousElementSibling", "scrollHeight");