Javascript 根据键值对数组进行分组，返回对象而不是数组

我在Stack Overflow上看到了许多关于这个主题的问题，然而，它们似乎都返回了单个对象.(不是我想要的)

我下面有一个数组；

const locations = [
    {"city": "London", "district": "Brixton", "id": "Eue3uFjUHKi6wh73QZLX"},
    {"city": "Manchester", "district": "Bury", "id": "QZiiUBgzZaJt2HcahELT"},
    {"city": "London", "district": "Hackney", "id": "v2itdyO4IPXAMhIU8wce"}
]

我想将此数组映射为基于"city"键的部分.

我的预期yields 是；

 [
    {
       city: "London",
       data: [
          {
             city: "London",
             district: "Brixton",
             id: "Eue3uFjUHKi6wh73QZLX"
          },
          {
             city: "London",
             district: "Hackney",
             id: "v2itdyO4IPXAMhIU8wce"
          }
       ]
    },
    {
       city: "Manchester",
       data: [
          {
             city: "Manchester",
             district: "Bury",
             id: "QZiiUBgzZaJt2HcahELT"
          }
       ]
    }
 ]

我已经try 了下面的方法；

const groupedLocations = locations.reduce((groups, item) => {
  const { city } = item;
  if (!groups[city]) {
    groups[city] = [];
  }
  groups[city].push(item);
  return groups;
}, {});

但是，这返回的是对象而不是array.