Decrement value in mongodb

Question

I am creating a shopping application. Each user have wallet. Structure is like :

{ 
    \"userName\" : \"Gandalf the Grey\",
    \"wallet\" : 100,
    \"orderHi         


        

Answer 1

You can use $inc operator

db.collection('users').updateOne(
  { 'userName': controller.userName },
  { '$inc': { 'wallet': -product.cost } }
)