如何使用map()、reduce()和filter()来简化javascript嵌套数组？
如何使用map()、reduce()和filter()来简化javascript嵌套数组？
提问于 2019-06-26 05:24:54
首先，我是一个Javascript，ES6等的新手，我来自Java背景。我有一个复杂的javascript数组结构(示例如下)，我试图将这个数组转换成一个映射(类似于Java的方法，键值对之类的东西)，key是权限名称(例如，关于下面的javascript数组示例，KEY-1，KEY-2，KEY-3，KEY-4，KEY-5 )而value是实际权限的逗号分隔值。我可以通过在嵌套数组中循环b来实现，但是循环是我在这里试图避免的，并且希望使用map()/reduce()/filter()
以下是地图应如何包含数据的示例。由于KEY-2在两个数组中都存在，它们将被重写为一个(这是非常好的)
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KEY名称硬编码到我的代码中(如KEY-1、KEY-2等)。
我遵循了这篇文章，下面是我尝试过的，但我想，我正在努力在一个复杂的https://www.freecodecamp.org/news/15-useful-javascript-examples-of-map-reduce-and-filter-74cbbb5e0a1f/数组上正确地使用/reduce()。我更喜欢普通的Javascript/ES6解决方案(没有JQuery请)。
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)这里的任何帮助都将受到高度的感谢。谢谢
回答 3
Stack Overflow用户
回答已采纳
发布于 2019-06-26 08:31:56
因为您不需要担心其他键/值，所以首先需要创建一个包含所有permissions对象的数组。然后从该数组中提取属性，并使用集合保持数组的唯一性：
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; }
Stack Overflow用户
发布于 2019-06-26 05:48:12
您可以使用flatMap和reduce的组合来完成(尽管flatMap还不是所有浏览器都支持)：
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);
如果键的权限数组可能非常大，还可以考虑在累加器中的每个键旁边使用Set。
Stack Overflow用户
发布于 2019-06-26 05:42:52
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));页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/56762203
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