Database
[{animals:[{type:"dog",IQ:100},{type:"cat",IQ:110},{type:"bear",IQ:120},]}]
Query
db.collection.update({},[{"$set":{"animals":{"$map":{"input":"$animals","in":{"$switch":{"branches":[{"case":{"$eq":["$$this.type","dog"]},"then":{$mergeObjects:["$$this",{IQ:200}]}},{"case":{"$eq":["$$this.type","cat"]},"then":{$mergeObjects:["$$this",{IQ:300}]}}],default:"$$this"}}}}}}])