There is such a group of data, want to find to the second group, namely array type data, the appropriate query conditions

{
 "_id" : ObjectId("57986ddab806c2490e67abdc"),
 "test" : "this a test",
 }
 
 {
 "_id" : ObjectId("57986ddab806c2490e67abdd"),
 "test" : [
 "this a test"
 ],
 }

Use $type yourself, but only find to

//find
 db.data.find( { test: { $type: “array” } } )
 //result
 {
 "_id" : ObjectId("57986ddab806c2490e67abdd"),
 "test" : [
 [
 "this a test"
 ]
 ],
 }