如何使用 map()、reduce() 和 filter() 简化 javascript 嵌套数组？

Question

首先，我是 Javascript、ES6 等的新手，我来自 Java 背景。 我有一个复杂的 javascript 数组结构（下面给出的示例）， 我正在尝试将此数组转换为映射（类似于 Java 的键值对类型），键是权限名称（例如 KEY-1、KEY-2、KEY-3、KEY-4、KEY- 5 关于下面的 javascript 数组示例），而 value 是实际权限的逗号分隔值。我可以通过通过嵌套数组循环 b 来实现它，但是循环是我在这里试图避免的，并且想要使用 map()/reduce()/filter()

以下是地图应如何包含数据的示例。由于 KEY-2 存在于两个数组中，因此它们将被覆盖为一个（这非常好）

KEY-1 = ["Roles.Create","Roles.Edit"]
KEY-2 = ["API-Admin.Create","API-Admin.Edit","API-Admin.Read"]
KEY-3 = ["Roles.Create","Roles.Edit"]
KEY-4 = ["Users.Read"]      
KEY-5 = ["Roles.Create","Roles.Edit"]

Javascript 数组

const teamArr = [
  {
    "name":"Team1",
    "accountId":"Billing",
    "teamId":"12345",
    "permissions": {
        "KEY-1": [
            "Roles.Create",
            "Roles.Edit"
        ],
        "KEY-2": [
            "API-Admin.Create",
            "API-Admin.Edit",
            "API-Admin.Read"
        ],
        "KEY-3": [
          "Roles.Create",
          "Roles.Edit"
        ]
     }
   },
   {
     "name":"Team2",
     "accountId":"Sales",
     "teamId":"6789",
     "permissions": {
         "KEY-4": [
             "Users.Read"
         ],
         "KEY-2": [
            "API-Admin.Create",
            "API-Admin.Edit",
            "API-Admin.Read"
        ],
         "KEY-5": [
           "Roles.Create",
           "Roles.Edit"
         ]
      }
   }
]

KEY-1、KEY-2、KEY-3、KEY-4、KEY-5 等都是动态生成的，所以我不能将这些键名硬编码到我的代码中（如 KEY-1、KEY-2 等）。 )

我关注了这个帖子https://www.freecodecamp.org/news/15-useful-javascript-examples-of-map-reduce-and-filter-74cbbb5e0a1f/ 以下是我尝试过的，但我想，我正在努力在复杂的 javascript 数组上正确使用 sort()/reduce()。我更喜欢普通的 Javascript/ES6 解决方案（没有 JQuery pls）。

const sorted = test.sort((a, b) => a.permissions - b.permissions);
// Using reduce:
dict = sorted.reduce(
    (dict, el, index) => (dict[el.permissions] = sorted.length - index, dict),
    {}
);

console.log(dict)

这里的任何帮助将不胜感激。谢谢

Answer 1

由于您不需要担心其他键/值，因此您需要首先创建一个包含所有 permissions 对象的数组。然后从该数组中提取属性，使用 Set 保持数组的唯一性：

const teamArr = [{"name":"Team1","accountId":"Billing","teamId":"12345","permissions":{"KEY-1":["Roles.Create","Roles.Edit"],"KEY-2":["API-Admin.Create","API-Admin.Edit","API-Admin.Read"],"KEY-3":["Roles.Create","Roles.Edit"]}},{"name":"Team2","accountId":"Sales","teamId":"6789","permissions":{"KEY-4":["Users.Read"],"KEY-2":["API-Admin.Create","API-Admin.Edit","API-Admin.Read"],"KEY-5":["Roles.Create","Roles.Edit"]}}];
const res = teamArr.flatMap(({ permissions }) => Object.entries(permissions)).reduce((a, [k, v]) => ((a[k] = [...new Set(((a[k] = a[k] || []).push(...v), a[k]))], a)), {});
console.log(res);

.as-console-wrapper { max-height: 100% !important; top: auto; }

更详细的版本：

const teamArr = [{"name":"Team1","accountId":"Billing","teamId":"12345","permissions":{"KEY-1":["Roles.Create","Roles.Edit"],"KEY-2":["API-Admin.Create","API-Admin.Edit","API-Admin.Read"],"KEY-3":["Roles.Create","Roles.Edit"]}},{"name":"Team2","accountId":"Sales","teamId":"6789","permissions":{"KEY-4":["Users.Read"],"KEY-2":["API-Admin.Create","API-Admin.Edit","API-Admin.Read"],"KEY-5":["Roles.Create","Roles.Edit"]}}];
const permissions = teamArr.map(({ permissions }) => permissions);
const res = permissions.flatMap(Object.entries).reduce((a, [k, v]) => {
  a[k] = a[k] || [];
  a[k].push(...v);
  a[k] = [...new Set(a[k])];
  return a;
}, {});
console.log(res);

.as-console-wrapper { max-height: 100% !important; top: auto; }

Answer 2

您可以结合使用flatMap 和reduce（尽管并非所有浏览器都支持flatMap）：

const teamArr = [{
    "name": "Team1",
    "accountId": "Billing",
    "teamId": "12345",
    "permissions": {
      "KEY-1": [
        "Roles.Create",
        "Roles.Edit"
      ],
      "KEY-2": [
        "API-Admin.Create",
        "API-Admin.Edit",
        "API-Admin.Read"
      ],
      "KEY-3": [
        "Roles.Create",
        "Roles.Edit"
      ]
    }
  },
  {
    "name": "Team2",
    "accountId": "Sales",
    "teamId": "6789",
    "permissions": {
      "KEY-4": [
        "Users.Read"
      ],
      "KEY-2": [
        "API-Admin.Create",
        "API-Admin.Edit",
        "API-Admin.Read"
      ],
      "KEY-5": [
        "Roles.Create",
        "Roles.Edit"
      ]
    }
  }
]

const result = teamArr
  .flatMap(t => Object.entries(t.permissions))
  .reduce((acc, [key, permissions]) => {
    acc[key] = acc[key] || [];
    acc[key].push(...permissions.filter(p => !acc[key].includes(p)));
    return acc;
  }, {});
  
console.log(result);

如果某个键的权限数组可能非常大，您还可以考虑在累加器中的每个键旁边使用Set。

Answer 3

const teamArr = [
  {
    "name":"Team1",
    "accountId":"Billing",
    "teamId":"12345",
    "permissions": {
        "KEY-1": [
            "Roles.Create",
            "Roles.Edit"
        ],
        "KEY-2": [
            "API-Admin.Create",
            "API-Admin.Edit",
            "API-Admin.Read"
        ],
        "KEY-3": [
          "Roles.Create",
          "Roles.Edit"
        ]
     }
   },
   {
     "name":"Team2",
     "accountId":"Sales",
     "teamId":"6789",
     "permissions": {
         "KEY-4": [
             "Users.Read"
         ],
         "KEY-2": [
            "API-Admin.Create",
            "API-Admin.Edit",
            "API-Admin.Read"
        ],
         "KEY-5": [
           "Roles.Create",
           "Roles.Edit"
         ]
      }
   }
];



function extractPermissions(obj) {
    const perms = {};
    obj.forEach(entry => {
        if (!entry['permissions']) {
            return;
        }
        Object.keys(entry.permissions).forEach(key => {
            if (!perms[key]) {
                perms[key] = [];
            }
            entry.permissions[key].forEach(value => {
                if (!perms[key].some(val => val === value)) {
                    perms[key].push(value);
                }
            });
        });
    });
    return perms;
}
console.log(JSON.stringify(extractPermissions(teamArr), null, 2));