如何把数组对象处理为{ 浙江: ['杭州', '宁波', '温州', '嘉兴', '湖州'], 福建: ['福州', '厦门', '莆田', '三明', '泉州'], };

假设数组对象为：

const cities = [
  { province: '浙江', city: '杭州' },
  { province: '浙江', city: '宁波' },
  { province: '浙江', city: '温州' },
  { province: '浙江', city: '嘉兴' },
  { province: '浙江', city: '湖州' },
  { province: '福建', city: '福州' },
  { province: '福建', city: '厦门' },
  { province: '福建', city: '莆田' },
  { province: '福建', city: '三明' },
  { province: '福建', city: '泉州' },
];

可以使用 reduce 方法进行处理：

const result = cities.reduce((acc, cur) => {
  if (!acc[cur.province]) {
    acc[cur.province] = [cur.city];
  } else {
    acc[cur.province].push(cur.city);
  }
  return acc;
}, {});

最终得到的结果为：

{
  "浙江": ["杭州", "宁波", "温州", "嘉兴", "湖州"],
  "福建": ["福州", "厦门", "莆田", "三明", "泉州"]
}