[{shop:["A","B","C","D"],fruits:["banana","apple","kiwi"],region:["north","south","west","east"]}]

db.collection.aggregate([{$facet:{shop:[{$project:{shop:1}},{$unwind:"$shop"},{$group:{_id:"$shop",count:{$sum:1}}},{$project:{_id:0,k:"$_id",v:"$count"}}],fruits:[{$project:{fruits:1}},{$unwind:"$fruits"},{$group:{_id:"$fruits",count:{$sum:1}}},{$project:{_id:0,k:"$_id",v:"$count"}}],region:[{$project:{region:1}},{$unwind:"$region"},{$group:{_id:"$region",count:{$sum:1}}},{$project:{_id:0,k:"$_id",v:"$count"}}]}},{$project:{shop:{$arrayToObject:"$shop"},fruits:{$arrayToObject:"$fruits"},region:{$arrayToObject:"$region"}}}])