Mongoose 将嵌套排序对象传递给查询

Question

我有以下查询，作为硬编码字符串传递：

router.get( '/rank/:round/', ( req, res, next ) => {

    let query = { "score.0.r1" : -1};

    Team.find( {} )
        .sort( query )
        .then( teams => {
            return res.json( teams );
        } ).catch( next );
} );

但是，当我尝试像这样传递我的路由参数 :round 时：

let query = { "score.0.r" + req.params.round : -1};

它不起作用（它返回一个未排序的列表）。

我也试过了：

let sort = "score.0['r" + req.params.round + "']";
let query = { sort : -1 };

再次，没有成功。这是我正在查询的示例文档：

 {
    "_id" : ObjectId("57cc7665a43bf14533b0d78a"),
    "name" : “Joe Bloggs”,
    "score" : [ 
        {
            "r5" : 23,
            "r4" : 20,
            "r3" : 25,
            "r2" : 23,
            "r1" : 40
        }
    ]
}

...我试图按 r（圆形）分数返回排序列表。

Answer 1

我认为这应该可行。

let sort =  "score.0.r" + req.params.round
let query = { [sort] : -1 };

它只是javascript，默认情况下javascript中对象的键被转换为字符串

let query = { "score.0.r" + req.params.round : -1};
query; //{ String("score.0.r" + req.params.round) : -1} 
       //{ '"score.0.r" + req.params.round': -1}

let sort = "score.0['r" + req.params.round + "']";
let query = { sort : -1 };
query; // { String(sort) : -1} => {"sort": -1}

要在javascript对象中做动态键，只需用括号括起来键

var string = "any_string" + variable
var obj = { [string] : "anyvalue"} 
//this will tell javascript that the key is variable not a string