MongoDB javascript `"$function"` 未在 mongoplayground.net 中返回预期值

Question

N.B.: 这是我写的第一个javascript函数。我的问题受到 another question 询问 MongoDB 文档中的递归下降的启发。

我在 jsfiddle.net and it works, but when I try it on mongoplayground.net 上试过这个功能，它不起作用。

输入集合：

[
  {
    "_id": 0,
    "text": "Node1",
    "children": [
      {
        "text": "Node2",
        "children": []
      },
      {
        "text": "Node3",
        "children": [
          {
            "text": "Node4",
            "children": [
              {
                "text": "Node5",
                "children": []
              },
              {
                "text": "Node6",
                "children": []
              }
            ]
          },
          {
            "text": "Node7",
            "children": []
          }
        ]
      }
    ]
  }
]

mongoplayground.net聚合管道：

db.collection.aggregate([
  {
    "$set": {
      "texts": {
        "$function": {
          "body": "function(t, n) {function drill(t, n) {if (n.length > 0) {for (let elem of n) {t.push(elem.text); drill(t, elem.children)}} return t};drill(t,n)}",
          "args": [
            [
              "$text"
            ],
            "$children"
          ],
          "lang": "js"
        }
      }
    }
  }
])

jsfiddle.net 输出期望的结果，["Node1", "Node2", "Node3", "Node4", "Node5", "Node6", "Node7"]，但 mongoplayground.net 将 "texts" 设置为 null。

有没有办法修复 MongoDB "$function" 或者这是 mongoplayground.net 或 MongoDB 的限制？

Answer 1

如何仅删除外部函数以获得您想要的结果：

    db.collection.aggregate([
  {
    "$addFields": {
      "texts": {
        "$function": {
          "body": "function drill(t, n) {if (n.length > 0) {for (let elem of n) {t.push(elem.text); drill(t, elem.children)}} return t};",
          "args": [
            [
              "$text"
            ],
            "$children"
          ],
          "lang": "js"
        }
      }
    }
  }
])

你可以看到它有效here

MongoDB javascript `"$function"` 未在 mongoplayground.net 中返回预期值

MongoDB javascript `"$function"` not returning expected value in mongoplayground.net

javascript

recursive-descent

mongodb

mongodb-query