MongoDb aggregation if else

Syntax:

{$cond: [<expression>, <true>, <false>] }

Example as given below

db.Customers.aggregate([

    { "$project": {

        "name": 1,

        "customer": {

            "$cond": {

                "if": { "$eq": [ "$Age", 25 ] },

                "then": "YG",

                "else": {

                    "$cond": {

                        "if": { "$eq": ["$Age", 45]},

                        "then: "MYG",

                        "else": "SCZ"

                    }

                }

            }

        }

    }},

   { "$sort": { CreatedDate: 1 }}

]);

For more detail, go to  https://docs.mongodb.com/