Spread Syntax For Nested Javascript Object With Dynamic Properties For Grouping

const data = [{year:2019,month:1,id:'xd1'}, {year:2019,month:1,id:'xd2'}, {year:2019,month:1,id:'xd4'}, {year:2019,month:2,id:'xd1'}, {year:2018,month:1,id:'rd3'}, {year:2018,

Solution 1:

Just add some sh*t and sticks:

const data = [{year:2019,month:1,id:"xd1"},
 {year:2019,month:1,id:"xd2"},
 {year:2019,month:1,id:"xd4"},
 {year:2019,month:2,id:"xd1"},
 {year:2018,month:1,id:"rd3"},
 {year:2018,month:2,id:"rd6"},
 {year:2018,month:2,id:"rd7"}
]

const result = data.reduce((state, d) => {
    return {
        ...state,
        [d.year]: {
            ...state[d.year],
            [d.month]: [
                ...((state[d.year]||{})[d.month]||[]),
                d.id]
        }
    }
},{})

console.log(result);