function myFunction(myObject, myArray) {
  const value = myArray.pop();
  const lastKey = myArray.pop();
  const innerObject = myArray.reduce((obj, key) => {
    if (!(obj[key] instanceof Object)) {
      obj[key] = {};
    }
    return obj[key];
  }, myObject);
  innerObject[lastKey] = value;
}