Javascript 如何在返回结果中创建新字段，并根据使用Mongoose的条件在其中设置值？

我有一个叫“动物”的MongoBD收藏

    [
        {
            _id:ObjectId("5f3ecddd7fe1af0c68614605"),
            status: "wild",
            name: "Wolf"
        },
        {
            _id:ObjectId("5f3ecddd7fe1af0c68614606"),
            status: "domestic",
            name: "Dog"
        },
        {
            _id:ObjectId("5f3ecddd7fe1af0c68614607"),
            status: "domestic",
            name: "Pussy Cat"
        },
        {
            _id:ObjectId("5f3ecddd7fe1af0c68614608"),
            status: "wild",
            name: "Lion"
        },
        {
            _id:ObjectId("5f3ecddd7fe1af0c68614609"),
            status: "wild",
            name: "Snake"
        }
    ]

我想使用mongoose中的聚合管道查询该集合，并使用一个新字段返回结果，该字段根据文档中的

status

字段对其进行分类。例如，具有

状态的文档：“野生”

获取新字段

new\u字段：“坚韧的森林动物”

然后，具有

状态的文档：“家养”

获得新字段

新字段：“友好邻里动物”

我想要这样的结果

[
    {
        _id: "5f3ecddd7fe1af0c68614605",
        status: "wild",
        name: "Wolf",
        new_field: "Tough Forest Animal"
    },
    {
        _id: "5f3ecddd7fe1af0c68614606",
        status: "domestic",
        name: "Dog",
        new_field: "Friendly Neighborhood Animal"
    },
    {
        _id: "5f3ecddd7fe1af0c68614607",
        status: "domestic",
        name: "Pussy Cat",
        new_field: "Friendly Neighborhood Animal"
    },
    {
        _id: "5f3ecddd7fe1af0c68614608",
        status: "wild",
        name: "Lion",
        new_field: "Tough Forest Animal"
    },
    {
        _id: "5f3ecddd7fe1af0c68614609",
        status: "wild",
        name: "Snake",
        new_field: "Tough Forest Animal"
    }
]

---

非常感谢所有给予我的帮助。谢谢你

我终于弄明白了。使用switch语句

AnimalsModel.aggregate([
    {
        $project: {

            "_id": 1,
            "status": 1,
            "name": 1,
            "new_field": {
                "$switch": {
                    "branches": [
                        { "case": { "$eq": [ "$status", "wild" ] }, "then": 'Tough Forest Animal' },
                        { "case": { "$eq": [ "$status", "domestic" ] }, "then": 'Friendly Neighborhood Animal' },
                    ],
                    "default": 'None of the above'
                }
            }
        }
    }
],function (error, animals) {
    console.log(animals)
});