Concat int en string array-velden die in verschillende arrays staan

U kunt onderstaande aggregatie gebruiken

db.collection.aggregate([
  { "$project": {
    "itemQtyList": {
      "$reduce": {
        "input": { "$range": [0, { "$size": "$sale.soldItems" }] },
        "initialValue": "",
        "in": {
          "$concat": [
            "$$value",
            { "$cond": [{ "$eq": ["$$this", 0] }, "", " \n "] },
            { "$toString": {
              "$arrayElemAt": [
                "$sale.soldItems.qty",
                "$$this"
              ]
            }},
            " ",
            { "$arrayElemAt": ["$sale.items.unit", "$$this"] }
          ]
        }
      }
    }
  }}
])

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