db={user:[{_id:ObjectId("62b6a1ad5bb65d5a1e2c0dcc"),name:"Admin",username:"Admin",email:"admin@admin.com",password:"$2b$10$qVWp8HZdId/cjVOXwiNLyeyv0jNo7BMFqFEKwNQniusazABp6s216",profilePicture:"",coverPicture:"",followers:[ObjectId("62b6abc96e3985aa5b2848b8"),ObjectId("62b6abb96e3985aa5b2848b0"),ObjectId("62b6abbf6e3985aa5b2848b2"),],following:[],isAdmin:false,createdAt:"2022-06-25T05:48:29.095Z",updatedAt:"2022-06-25T07:45:33.290Z","__v":0,}],post:[{_id:ObjectId("62b6eaba03ca17b3eb642e24"),userId:ObjectId("62b6a1ad5bb65d5a1e2c0dcc"),description:"one",image:"https://firebasestorage.googleapis.com/v0......",tags:[],likes:[],createdAt:"2022-06-25T11:00:10.108Z",updatedAt:"2022-06-25T11:00:10.108Z","__v":0,},{_id:ObjectId("62b6eaba03ca17b3eb642e25"),userId:ObjectId("62b6abc96e3985aa5b2848b8"),description:"two",image:"https://firebasestorage.googleapis.com/v0......",tags:[],likes:[],createdAt:"2022-06-25T11:00:10.108Z",updatedAt:"2022-06-25T11:00:10.108Z","__v":0,},{_id:ObjectId("62b6eaba03ca17b3eb642e26"),userId:ObjectId("62b6abb96e3985aa5b2848b0"),description:"three",image:"https://firebasestorage.googleapis.com/v0......",tags:[],likes:[],createdAt:"2022-06-25T11:00:10.108Z",updatedAt:"2022-06-25T11:00:10.108Z","__v":0,},{_id:ObjectId("62b6eaba03ca17b3eb642e27"),userId:ObjectId("62b6abb96e3985aa5b284999"),description:"four",image:"https://firebasestorage.googleapis.com/v0......",tags:[],likes:[],createdAt:"2022-06-25T11:00:10.108Z",updatedAt:"2022-06-25T11:00:10.108Z","__v":0,}]}

db.user.aggregate([{$lookup:{from:"post",localField:"_id",foreignField:"userId",as:"my-post"}},{$lookup:{from:"post",localField:"followers",foreignField:"userId",as:"follow-post"}}])