MongoDB aggregate Lookup remove array

I am currently using an aggregate lookup method from mongoose and it works:

const data = await this.messageModel.aggregate([
    {
        $match: { channel_id: channel_id },
    },
    {
        $limit: limit ? limit : 1000,
    },
]).lookup({
    from: 'users',
    localField: 'author',
    foreignField: 'id',
    as: 'author',
    pipeline: [
        { $project: { _id: 0, password: 0, email: 0, __v: 0 } }
    ],
});

The data returns an array of object like this

{
        "_id": "622861fe264eaed05a32bb2d",
        "channel_id": "5850473746686541647",
        "author": [
            {
                "username": "UnusualAbsurd",
                "status": "Working...",
                "createdAt": "2022-03-08T14:02:53.728Z",
                "id": "1"
            }
        ],
        "id": "5850638795510120271",
        "createdAt": "2022-03-09T08:14:54.228Z",
        "attachments": [],
        "content": "zazaza",
        "__v": 0
}

Now the problem is, the author object that I used the lookup() method on returns as an array. How do I make it not return as an array?

Answers:

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Method 1

You can use $unwind after lookup like this:

{$unwind: '$author'}

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