如何按对象属性对数组进行分组

const items = [
  { name: 'item1', category: 'A' },
  { name: 'item2', category: 'B' },
  { name: 'item3', category: 'A' },
  { name: 'item4', category: 'C' },
  { name: 'item5', category: 'B' }
];

const groupedItems = items.reduce((accumulator, currentItem) => {
  // 如果累加器中还没有当前项的分类，就创建一个空数组
  if (!accumulator[currentItem.category]) {
    accumulator[currentItem.category] = [];
  }
  // 将当前项添加到对应分类的数组中
  accumulator[currentItem.category].push(currentItem);
  return accumulator;
}, {});

console.log(groupedItems);

{
  A: [
    { name: 'item1', category: 'A' },
    { name: 'item3', category: 'A' }
  ],
  B: [
    { name: 'item2', category: 'B' },
    { name: 'item5', category: 'B' }
  ],
  C: [
    { name: 'item4', category: 'C' }
  ]
}

const safeGroupedItems = items.reduce((accumulator, currentItem) => {
  const category = currentItem.category || 'Unknown';
  if (!accumulator[category]) {
    accumulator[category] = [];
  }
  accumulator[category].push(currentItem);
  return accumulator;
}, {});

console.log(safeGroupedItems);