multi-level nesting (aka groupby) in javascript using d3.js (adapted from http://learnjsdata.com/group_data.html)

javascript-nested-groupby-with-aggregation

var expect = require('chai').expect;
var d3 = require('d3');

describe('app', function () {
  
  var myData = [
            { countryCode: 'DE', areaName: 'DE1', speciesName: 's1', totalScore: 1000 },
            { countryCode: 'DE', areaName: 'DE1', speciesName: 's2', totalScore: 2000 },
            { countryCode: 'DE', areaName: 'DE1', speciesName: 's3', totalScore: 3000 },
            { countryCode: 'DE', areaName: 'DE2', speciesName: 's1', totalScore: 1000 },
            { countryCode: 'DE', areaName: 'DE2', speciesName: 's2', totalScore: 2000 },
            { countryCode: 'DE', areaName: 'DE2', speciesName: 's3', totalScore: 3000 },
            { countryCode: 'DE', areaName: 'DE3', speciesName: 's1', totalScore: 1000 },
            { countryCode: 'DE', areaName: 'DE3', speciesName: 's2', totalScore: 2000 },
            { countryCode: 'DE', areaName: 'DE3', speciesName: 's3', totalScore: 3000 },

            { countryCode: 'ES', areaName: 'ES1', speciesName: 's1', totalScore: 1000 },
            { countryCode: 'ES', areaName: 'ES1', speciesName: 's2', totalScore: 2000 },
            { countryCode: 'ES', areaName: 'ES1', speciesName: 's3', totalScore: 3000 },
            { countryCode: 'ES', areaName: 'ES2', speciesName: 's1', totalScore: 1000 },
            { countryCode: 'ES', areaName: 'ES2', speciesName: 's2', totalScore: 2000 },
            { countryCode: 'ES', areaName: 'ES2', speciesName: 's3', totalScore: 3000 },
            { countryCode: 'ES', areaName: 'ES3', speciesName: 's1', totalScore: 1000 },
            { countryCode: 'ES', areaName: 'ES3', speciesName: 's2', totalScore: 2000 },
            { countryCode: 'ES', areaName: 'ES3', speciesName: 's3', totalScore: 3000 },

            { countryCode: 'JP', areaName: 'JP1', speciesName: 's1', totalScore: 1000 },
            { countryCode: 'JP', areaName: 'JP1', speciesName: 's2', totalScore: 2000 },
            { countryCode: 'JP', areaName: 'JP1', speciesName: 's3', totalScore: 3000 },
            { countryCode: 'JP', areaName: 'JP2', speciesName: 's1', totalScore: 1000 },
            { countryCode: 'JP', areaName: 'JP2', speciesName: 's2', totalScore: 2000 },
            { countryCode: 'JP', areaName: 'JP2', speciesName: 's3', totalScore: 3000 },
            { countryCode: 'JP', areaName: 'JP3', speciesName: 's1', totalScore: 1000 },
            { countryCode: 'JP', areaName: 'JP3', speciesName: 's2', totalScore: 2000 },
            { countryCode: 'JP', areaName: 'JP3', speciesName: 's3', totalScore: 3000 }
        ];

  
  
  it('should do what I want (using d3)', function () {
      
        var scoreBySpeciesAndCountry = d3.nest()
            .key(function (d) { return d.speciesName; })
            .key(function (d) { return d.countryCode; })
            .rollup(function (v) { return d3.sum(v, function (d) { return d.totalScore; }) })
            .map(myData);
        
        expect(scoreBySpeciesAndCountry).to.eql(
            {
                s1: { DE: 3000, ES: 3000, JP: 3000 },
                s2: { DE: 6000, ES: 6000, JP: 6000 },
                s3: { DE: 9000, ES: 9000, JP: 9000 }
            }
        )
    });
    
  
    it('should do what I want (vanilla js solution....)', function () {
        
        var myMap = function (d) {

            function uniq(value, index, self) {
                return self.indexOf(value) === index;
            };

            var output = d.map(obj => obj.speciesName).filter(uniq).map(speciesName => {
                return [speciesName, d.filter(obj => obj.speciesName == speciesName).map(obj => obj.countryCode).filter(uniq).map(countryCode => {
                    return [countryCode, d.filter(obj => obj.speciesName == speciesName && obj.countryCode == countryCode).reduce((sum, obj) => sum + obj.totalScore, 0)];
                }).reduce((hash, result) => (hash[result[0]] = result[1]) && hash, {})];
            }).reduce((hash, result) => (hash[result[0]] = result[1]) && hash, {});

            return output;
        };

        expect(myMap(sampleData)).to.eql(
            {
                s1: { DE: 3000, ES: 3000, JP: 3000 },
                s2: { DE: 6000, ES: 6000, JP: 6000 },
                s3: { DE: 9000, ES: 9000, JP: 9000 }
            }
        );
    });
  
});