mongodb - How to retrieve array value index wise -

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how retrieve array value index-wise in mongodb? in below query, want computers answer:

> db.customers.find({}, { likes : { $slice: 1}}).pretty() {         "_id" : objectid("57709662a93160be074de74a"),         "name" : "john",         "age" : "40",         "likes" : [                 "computers"         ] }

is looking for

db.customers.aggregate([{$project:{_id:0,selected:{$slice:["$likes", 1]}}},{$unwind:"$selected"}]);

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