如何在Javascript中重组对象？

Question

我的位置列表：

[ 
{ 
    "id": 1, 
    "name": "Location 1", 
    "city": { 
     "id": 7, 
     "name": "Phoenix", 
    } 
}, 
{ 
    "id": 2, 
    "name": "Location 2", 
    "city": { 
     "id": 7, 
     "name": "Phoenix", 
    } 
}, 
{ 
    "id": 3, 
    "name": "Location 3", 
    "city": { 
     "id": 11, 
     "name": "Los Angeles", 
    } 
} 
] 

出的，我想创造城市的数组，每个城市有来自城市的位置。

结果举例：

[ 
    { 
     "id": 7, 
     "name": "Phoenix", 
     "locations": [ 
       // location objects from Phoenix (Location 1 and Location 2) 
      { 
       "id": 1, 
       "name": "Location 1", 
       "city": { 
        "id": 7, 
        "name": "Phoenix", 
       } 
      }, 
      { 
       "id": 2, 
       "name": "Location 2", 
       "city": { 
        "id": 7, 
        "name": "Phoenix", 
        } 
       } 
     ] 
    }, 
    { 
     "id": 11, 
     "name": "Los Angeles", 
     "locations": [ 
       // location objects from Los Angeles (Location 3) 
      { 
       "id": 3, 
       "name": "Location 3", 
       "city": { 
        "id": 11, 
        "name": "Los Angeles", 
       } 
      } 
     ] 
    } 
] 

我一直在使用.map()和.filter()获得唯一值的城市阵列尝试。它并没有返回整个city（return item.city）的唯一，不同的值，所以我只使用name属性（return item.city.name），因为我并不真正在意城市ID。我的独特的城市名称的数组：

var cities = data.map(function (item) { 
    return item.city.name; 
}).filter(function (value, index, self) { 
    return self.indexOf(value) === index; 
}); 

现在我卡在构建阵列将列出位置为每个城市的属性。预先感谢您...

Answer 1

我会首先创建一个对象，其中键设置为城市的id。然后，如果您需要数组中的这些对象，则只需通过键调用映射。例如创建锁定以ID对象：

var arr = [{"id": 1,"name": "Location 1","city": {"id": 7,"name": "Phoenix",}},{"id": 2,"name": "Location 2","city": {"id": 7,"name": "Phoenix",}},{"id": 3,"name": "Location 3","city": {"id": 11,"name": "Los Angeles",}}] 
 

 
var obj = arr.reduce((a, c) => { 
 
    if (a[c.city.id]) a[c.city.id].push(c) 
 
    else a[c.city.id] = [c] 
 
    return a 
 
}, {}) 
 

 
console.log(obj)

现在你有一个干净的对象，如果你想要一个数组只需添加一个地图上的按键：

var arr = [{"id": 1,"name": "Location 1","city": {"id": 7,"name": "Phoenix",}},{"id": 2,"name": "Location 2","city": {"id": 7,"name": "Phoenix",}},{"id": 3,"name": "Location 3","city": {"id": 11,"name": "Los Angeles",}}] 
 

 
var obj = arr.reduce((a, c) => { 
 
    if (a[c.city.id]) a[c.city.id].locations.push(c) 
 
    else a[c.city.id] = {name: c.city.name, locations:[c]} 
 
    return a 
 
}, {}) 
 

 
var arr_version = Object.keys(obj).map(k => Object.assign({id: k}, obj[k])) 
 

 
console.log(arr_version)