How to check in mongodb aggregation that document has key which is an array whose second element exists or not?

I have mongodb document it has key which is an array. i want to check that the 2nd element in array exists or not. if exists then return the documents otherwise return no document.

example document :

{
 _id : "672d75267",
 name : "somename",
 arr : [1,2,3]
}


db.collection.aggregate([
 {
   $match : {
      $expr : {
        $arrayElemAt : ["$arr",2]
     }
   }
 }
])

>Solution :

Array index start from 0 that is why we have taken "arr.1"

db.collection.aggregate([
  {
    $match: {
      "arr.1": {
        "$exists": true
      }
    }
  },
])