Mongoose pass nested sort object to query

Question

I have the following query which, passed as a hard coded string works:

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 );
} );

However, when I try to pass in my route param :round like this:

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

It doesn't work (it returns an unsorted list).

I have also tried:

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

Again, with no success. Here is my an example document I am querying:

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

... where I am trying to return a sorted list by r (round) score.

vdj4y · Accepted Answer · 2016-09-07 21:52:13Z

2

I think this should work.

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

It's just javascript, by default object's key in javascript is converted to a string

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}

to do dynamic key in javascript object, just enclose the key with bracket

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

edited Sep 7, 2016 at 21:52

answered Sep 7, 2016 at 20:24

vdj4y

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1 Comment

Matt D. Webb Over a year ago

Genius! Thank you, I would never have thought of that. If you'd like to provide a short explanation with this I am sure it will be very useful for others too. :-)

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