get the mongodb data type in js script

db.foo.find();


_id    | type
-------------
10001     1
10002    'a'
10003    [1, 2, 3, 4]

As you know, the $type will match the type code in mongo query, like this:

db.foo.find({type: {$type: 4}});

_id | type

----------

10003, [1, 2, 3, 4]

and then, I write a javascript shell script called test.js

var curs = db.foo.find();
curs.forEach(showTypeCode);
function showTypeCode(cur) {
  print(cur.type + '-' + typeof(cur.type));
};

results:

1-number
a-string
1,2,3,4-object (this is an array, it's 4 in mongo)

here is my question, how can I get the array type code in the mongo shell