无法使用Object.keys（）在数组中获取JSON密钥

Question

I'm trying to retrieve all the keys off a query result into an array. Should be a super easy thing to do but somehow am not able to. Here's the snippet:

fromMongoDB = parent.posts[0]
returnedkeys = Object.keys(fromMongoDB);
console.log(fromMongoDB);
console.log('-----------------------------');
console.log(returnedkeys);

The data I'm receiving into fromMongoDB is an object with two key-value pairs:

{
   id: <some ID>,
   title: <some title>
}

Using Object.keys() , I intend to get an array of the two keys:

[
  id, title
]

But this is what I'm getting instead:

{ id: '5ba1f3e7cc546723422e62a4', title: 'A Title!' }
-----------------------------
[ '__parentArray',
  '__parent',
  '__index',
  '$__',
  'isNew',
  'errors',
  '_doc',
  '$init' ]

What am I doing wrong? Is fromMongoDB not a JSON object?

Answer 1

You can try below aggregation in mongodb 3.4.4 and above

db.collection.aggregate([
  { "$project": {
    "keys": {
      "$objectToArray": "$$ROOT"
    }
  }},
  { "$project": { "keys": "$keys.k" }}
])

Answer 2

尝试这样的事情：

Object.getOwnPropertyNames(fromMongoDB);

Answer 3

Try lean() function instead. Append .lean() to your query and then use Object.keys() to get an array of keys.