带和的ES6嵌套分组

const data = [
  { id: 1, group: 'A' },
  { id: 2, group: 'B' },
  { id: 3, group: 'A' },
  { id: 4, group: 'B' },
  { id: 5, group: 'C' },
];

const groupedData = data.reduce((result, item) => {
  const { group } = item;
  if (!result.has(group)) {
    result.set(group, []);
  }
  result.get(group).push(item);
  return result;
}, new Map());

console.log(groupedData);

Map {
  'A' => [
    { id: 1, group: 'A' },
    { id: 3, group: 'A' }
  ],
  'B' => [
    { id: 2, group: 'B' },
    { id: 4, group: 'B' }
  ],
  'C' => [
    { id: 5, group: 'C' }
  ]
}

const data = {
  1: { group: 'A' },
  2: { group: 'B' },
  3: { group: 'A' },
  4: { group: 'B' },
  5: { group: 'C' },
};

const groupedData = Object.entries(data).reduce((result, [key, value]) => {
  const { group } = value;
  if (!result.has(group)) {
    result.set(group, {});
  }
  result.get(group)[key] = value;
  return result;
}, new Map());

console.log(groupedData);

Map {
  'A' => {
    '1' => { group: 'A' },
    '3' => { group: 'A' }
  },
  'B' => {
    '2' => { group: 'B' },
    '4' => { group: 'B' }
  },
  'C' => {
    '5' => { group: 'C' }
  }
}