如何获取数组中具有相同 id 的所有 object？

Question

I have an array of objects and I want to re-shape them based on a similar id "itemId"

array = [
{"choicesId": 2, "itemId": 40, "optionChoicesId": 4},
{"choicesId": 11, "itemId": 40, "optionChoicesId": 14},
{"choicesId": 141, "itemId": 41, "optionChoicesId": 104},
{"choicesId": 311, "itemId": 41, "optionChoicesId": 1987}
];

expected array

[
  {"id":40,"selected_ids":[{"choicesId":2},{"choicesId":11}]},
  {"id":41,"selected_ids":[{"choicesId":141},{"choicesId":311}]},
  ...
]

Answer 1

An easy approach can be like this

const mergeSelections = (selections) => {
  const groupedSelections = selections.reduce((acc, selection) => {
    const { itemId, choicesId } = selection;
    if (!acc[itemId]) {
      acc[itemId] = { id: itemId, selected_ids: [] };
    }
    acc[itemId].selected_ids.push({ choicesId });
    return acc;
  }, {});
  return Object.values(groupedSelections);
};

const array = [
  { choicesId: 2, itemId: 40, optionChoicesId: 4 },
  { choicesId: 11, itemId: 40, optionChoicesId: 14 },
  { choicesId: 141, itemId: 41, optionChoicesId: 104 },
  { choicesId: 311, itemId: 41, optionChoicesId: 1987 },
];

console.log(mergeSelections(array));