How can I create new fields in return results and set values in them on the basis of conditions using Mongoose?
I finally firgured it out. Use switch statements
AnimalsModel.aggregate([ { $project: { "_id": 1, "status": 1, "name": 1, "new_field": { "$switch": { "branches": [ { "case": { "$eq": [ "$status", "wild" ] }, "then": 'Tough Forest Animal' }, { "case": { "$eq": [ "$status", "domestic" ] }, "then": 'Friendly Neighborhood Animal' }, ], "default": 'None of the above' } } } }],function (error, animals) { console.log(animals)});