不能在MongoDB中获取子文档的id

Question

整个文档

{
   "_id": "5952e97a833244f2f94f1243",
   "name": "Starcups",
   "reviews": [
      {
         "author": "Simon Holmes",
         "id": "5952ea74833244f2f94f1244",
         "rating": 5,
         "timestamp": "2013-07-15T21:00:00.000Z",
         "reviewText": "What a great place.",
         "createdOn": "2017-07-02T00:32:40.449Z"
      },
      {
         "author": "Charlie Chaplin",
         "id": "5952eb61833244f2f94f1245",
         "rating": 3,
         "timestamp": "2013-07-15T21:00:00.000Z",
         "reviewText": "It was okay.",
         "createdOn": "2017-07-02T00:32:40.449Z"
      }
   ]
}

我有一个问题是在MongoDB中获取子文档的id。当我试图显示子文档的任何其他对象时，它工作正常。

例如

reviews[0].author 

会告诉我＆＃34; Simon Holmes＆＃34;值。

但是

reviews[0].id

会显示空

怎么办？如果不在子文档中按id搜索，我就无法返回需要的对象。