[{"name":["apple","banana","oranges","grapes"]},{"name":["apple","banana"]},{"name":["apple","oranges"]},{"name":["oranges","banana"]},{"name":["grapes","banana"]}]

db.collection.aggregate([{"$unwind":"$name"},{$group:{_id:"$name",count:{$sum:1}}},{$group:{_id:null,names:{$push:{k:"$_id",v:"$count"}}}},{$replaceRoot:{newRoot:{$arrayToObject:"$names"}}}])