$Filter Aggregator Operator In Mongodb

{
  $filter: {
    input: <array>,
    as: <variable>,
    cond: <condition>
  }
}

db.filterdemo.aggregate([
  {
    $project: {
      name: 1,
      highScores: {
        $filter: {
          input: "$scores",
          as: "score",
          cond: { $lt: ["$$score", 70] }
        }
      }
    }
  }
])

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