爱书法的程序猿

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用一个示例描述场景：
从下列数据中找出每个人的第一(id是1)爱好

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[
    {
        "_id": ObjectId("61975535a73483311a5670a7"),
        "name": "章三",
        "hobbies": [{ "id": 1, "name": "足球" }, { "id": 2, "name": "篮球" }]
    },
    {
        "_id": ObjectId("61975549a73483311a5670a8"),
        "name": "李四",
        "hobbies": [{ "id": 1, "name": "篮球" },{ "id": 2, "name": "羽毛球" }]
    },
    {
        "_id": ObjectId("61975564a73483311a5670a9"),
        "name": "王五",
        "hobbies": [{ "id": 1, "name": "书法" },{ "id": 2, "name": "篆刻" },{ "id": 3, "name": "围棋" }]
    }
]

最后期望得到的数据是

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[
    {
        "_id": ObjectId("61975535a73483311a5670a7"),
        "name": "章三",
        "hobbies": [{ "id": 1, "name": "足球" }]
    },
    {
        "_id": ObjectId("61975549a73483311a5670a8"),
        "name": "李四",
        "hobbies": [{ "id": 1, "name": "篮球" }]
    },
    {
        "_id": ObjectId("61975564a73483311a5670a9"),
        "name": "王五",
        "hobbies": [{ "id": 1, "name": "书法" }]
    }
]

使用 projection 数组占位符$

根据find的第二个参数 projection 过滤掉数组中不符合条件的元素，示例如下：

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这个小点每次都要搜索，记一下还是有必要的。

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