Using mongoose to add new field to existing document in mongodb through update method

Try the following code:

User.update(
     {uid: 'uid'}, 
     {vehicle_status : 'vehicleSatus' },
     {multi:true}, 
       function(err, numberAffected){  
       });

Also, make sure that you add vehicle_status to the schema.

Going through this solution in Year 2019.

Please note: collection.update is deprecated. Use updateOne, updateMany, or bulkWrite instead

According to new scenario always use {upsert:true}.

upsert - if set to true and no record matched to the query, replacement object is inserted as a new record.

   user.updateOne(
                 { email: req.body.email },
                 { $set: { name: 'Aaakash'}},{upsert:true}).then((result, err) => {
                    return res.status(200).json({ data: result, message:"Value Updated" });
                })