Merge array of objects based on overall key of object

Question

I have this array of objects

var worksSummaryDetailsArr = [
  {
    year: 2020,
    worksSummaryDetailsObj: [ [Object], [Object], [Object], [Object] ]
  },
  {
    year: 2021,
    worksSummaryDetailsObj: [ [Object], [Object], [Object], [Object] ]
  },
  {
    year: 2022,
    worksSummaryDetailsObj: [ [Object], [Object], [Object], [Object] ]
  },
  {
    year: 2021,
    worksSummaryDetailsObj: [ [Object], [Object], [Object], [Object] ]
  },
  {
    year: 2022,
    worksSummaryDetailsObj: [ [Object], [Object], [Object], [Object] ]
  }
]

I want to merge it into

  {
    year: 2020,
    worksSummaryDetailsObj: [ [Object], [Object], [Object], [Object] ]
  },
  {
    year: 2021,
    worksSummaryDetailsObj: [ [Object], [Object], [Object], [Object],[Object], [Object], [Object], [Object] ]
  },
  {
    year: 2022,
    worksSummaryDetailsObj: [ [Object], [Object], [Object], [Object],[Object], [Object], [Object], [Object] ]
  },

I have tried using the set function and mapping with the same year, and the output was the same years were merged correctly but the worksSummaryDetailsObj contains wrong data

here is my code

const r = [...new Set(worksSummaryDetailsArr.map((i) => i.year))].map((i) => ({
      year: i,
      worksSummaryDetailsObj: [...new Set(worksSummaryDetailsArr.filter(({ year: c }) => c === i))],
}));

console.log(r);

Answer 1

a simple reduce and array merge could achieve what you want

Object.values(
  worksSummaryDetailsArr.reduce((acc, arr) => {
    if (!acc[arr.year]) {
      acc[arr.year] = arr;
    } else {
      acc[arr.year] = {
        ...acc[arr.year],
        worksSummaryDetailsObj: [
          ...acc[arr.year].worksSummaryDetailsObj,
          ...arr.worksSummaryDetailsObj,
        ],
      };
    }
    return acc;
  }, {})
);