CODEWITHSUNDEEP
node.jsmongodbmongoose
MLWDEV
MLWDEV

Reputation: 65

MongoDB, Mongoose find all where _id is equal to key of object in array

Struggling with a query, I have a collection of users:

{
    "_id": "5c87bda25fdaasdf00171001e1",
    "name": "UserTwo Name",
    "email": "[email protected]"
},{
    "_id": "5c87bda25fda8b00171001e1",
    "name": "User Name",
    "email": "[email protected]"
}

I also have an array of objects containing a _userId key. I need to get all users where the _id of the user equals the value of _userId in my array.

[
    {_userId: "5c87bda25fda8b00171001e1"},
    {_userId: "5c87bda25fdaasdf00171001e1"},
]

What I have so far is:

User.find(
        {
            _id: { $in: req.body.users }
        }
    )

Which should be fine if req.body.users was just an array of ids, not array of objects.

Any help would be greatly appreciated. Thanks,

Upvotes: 1

Views: 1672

Answers (2)

Orelsanpls
Orelsanpls

Reputation: 23565

You have to turn the array 

[
    {_userId: "5c87bda25fda8b00171001e1"},
    {_userId: "5c87bda25fdaasdf00171001e1"},
]

into 

[
    "5c87bda25fda8b00171001e1",
    "5c87bda25fdaasdf00171001e1",
]

So how can we do that ?

Example 1 : using Array.map which iterate through the specified array, call a function and then create a new array with values being the ones returned by the function it called.

console.log([{
  _userId: "5c87bda25fda8b00171001e1",
},
{
  _userId: "5c87bda25fdaasdf00171001e1",
},
].map(x => x._userId));

Example 2 : Using a well known for loop and create the array ourselves

const arr = [{
  _userId: "5c87bda25fda8b00171001e1"
}, {
  _userId: "5c87bda25fdasdf0017101e1"
}, ];

const newArr = [];

for (let i = 0; i < arr.length; i += 1) {
  newArr.push(arr[i]._userId);
}

console.log(newArr);

PS : As @Ivan Vasiljevic proposed, when building the array of id, you can turn the string into ObjectID objects. It's not mandatory to do it using mongoose.find ; it is tho using mongoose.aggregate.

Upvotes: 0

Ivan Vasiljevic
Ivan Vasiljevic

Reputation: 5718

You should modify your query like this:

 User.find({
            _id: { $in: req.body.users.map(user => ObjectId(user._userId) }
 });

You need to convert _userId string to ObjectId. And that will be done with map function.

Upvotes: 5

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