[{"name":"Rahul","age":"15"},{"name":"Ajay","age":"25"},{"name":"Pinku","age":"43"},{"name":"Vinod","age":"30"},{"name":"Peter","age":"30"}]

db.collection.update({"name":{"$in":["Ajay","Pinku","Vinod","Rahul"]}},[{"$set":{"mark":{"$reduce":{"input":[{"name":"Ajay","marks":20},{"name":"Pinku","marks":12},{"name":"Vinod","marks":50},{"name":"Rahul","marks":80}],"initialValue":"$$REMOVE","in":{"$cond":[{"$eq":["$$this.name","$name"]},"$$this.marks","$$value"]}}}}}],{"multi":true})