mongodb: How to create _id for each array element?

Question

Is there a way that whenever I $push a new element in monodb array, a normal _id is added to it? I remember that mongoose was doing something like that automatically but now I am using mongodb's native js and it seems to be not inserting any _id.

Example:

chats.updateOne({_id: chat_id},
            {$push: {messages: 
                    {
                        message: data.message,
                        date: new Date(),
                    }}},
            function(err, response){}
)};

On executing, messages array should have regular _id field, message and date. Currently it only creates message and date.

Answer 1

You can use ObjectId() :

chats.updateOne({_id: chat_id},
            {$push: {messages: 
                    {
                        message: data.message,
                        date: new Date(),
                        _id: ObjectId()
                    }}},
            function(err, response){}
)};