拉属性对象作为父对象答案

【问题标题】：pull property object as parent object拉属性对象作为父对象
【发布时间】：2017-06-05 11:30:11
【问题描述】：

我有这组我无法控制的数据（它在某处托管 API，我无权访问）

let x = [
    {name: "james", age: 10, school: {id:1, name:"London"}},
    {name: "james_2", age: 11, school: {id:1, name:"London"}},
    {name: "john", age: 12, school: {id:2, name:"India"}},
    {name: "johnny", age: 56, school: {id:3, name:"USA"}}
]

如何先分组学校？我需要这样的格式

[{
    id:1,
    name: "London",
    data: [{
        name: "james", age: 10, school: {id:1, name:"London"
    },{name: "james_2", age: 11, school: {id:1, name:"London"}}]
}]

【问题讨论】：

标签： javascript ecmascript-6 lodash

【解决方案1】：

您可以使用_.groupBy() 并将结果映射回数组：

const data = [{"name":"james","age":10,"school":{"id":1,"name":"London"}},{"name":"james_2","age":11,"school":{"id":1,"name":"London"}},{"name":"john","age":12,"school":{"id":2,"name":"India"}},{"name":"johnny","age":56,"school":{"id":3,"name":"USA"}}];

const result = _(data)
  .groupBy('school.name')
  .map((group) => ({ // or Object.assign({}, group[0].school, { data: group });
    ...group[0].school,
    data: group
  }))
  .value();

console.log(result);

&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/lodash.js/4.17.4/lodash.min.js"&gt;&lt;/script&gt;

您可以在不使用 lodash 的情况下执行相同的操作，只需将 Array#reduce 与 Map 结合使用：

const data = [{"name":"james","age":10,"school":{"id":1,"name":"London"}},{"name":"james_2","age":11,"school":{"id":1,"name":"London"}},{"name":"john","age":12,"school":{"id":2,"name":"India"}},{"name":"johnny","age":56,"school":{"id":3,"name":"USA"}}];

const result = [...data.reduce((map, item) => {
  const school = map.get(item.school.name) || { // or Object.assign({}, { item.school }, { data: [] })
    ...item.school, data: [] 
  };
  
  school.data.push(item);
  
  map.set(item.school.name, school);
  
  return map;
}, new Map()).values()]

console.log(result);

【讨论】：

这是什么？ _（数据）
group[0].school 为什么在这里使用 [0]？
_(data) 启动 lodash 链。 group[0].school 用于从组的第一个元素中获取学校名称和 id。
group[0].school 怎么可能是第一个元素？我不明白jsfiddle.net/8y0bjzn9
欢迎 :) 顺便说一句 - 对象 rest/spread 需要一个 babel 插件，所以如果它对你不起作用，请改用 Object#assign：Object.assing({}, { item.school }, { data: [] })。

【解决方案2】：

您可以使用reduce() 方法：

let data = [
    {name: "james", age: 10, school: {id:1, name:"London"}},
    {name: "james_2", age: 11, school: {id:1, name:"London"}},
    {name: "john", age: 12, school: {id:2, name:"India"}},
    {name: "johnny", age: 56, school: {id:3, name:"USA"}}
];
let schools = data.reduce((acc, x) => {
  // Check if the school already exists
  let school = acc.find(y => y.id === x.school.id);
  if (!school) {
    // If not, the current school is the school of the current person
    school = x.school;
    school.data = [];
    acc.push(school);
  } else {
    // Prevent duplication of school objects with the same id
    x.school = school;
  }
  school.data.push(x);
  return acc;
}, []);
console.log(schools);

【讨论】：

【解决方案3】：

您可以将 lodash 库与 groupBy 一起使用

let x = [
    {name: "james", age: 10, school: {id:1, name:"London"}},
    {name: "james_2", age: 11, school: {id:1, name:"London"}},
    {name: "john", age: 12, school: {id:2, name:"India"}},
    {name: "johnny", age: 56, school: {id:3, name:"USA"}}
]


var result2 = _.chain(x)
    .groupBy(function(o){return o.school.name})
    .pairs()
    .map(function (currentItem) {
        return _.object(_.zip(["school", "name"], currentItem));
    })
    .value();
console.log(result2);

检查这个 jsFiddle :- http://jsfiddle.net/6yasy30a/

【讨论】：

成对？那是为了什么？
@AlanJenshen _pairs():- 为对象创建一个键值对的二维数组，例如[[键1，值1]，[键2，值2]]。 _.pairs({ '巴尼': 36, '弗雷德': 40 }); // => [['barney', 36], ['fred', 40]]（不保证迭代顺序）

【解决方案4】：

您可以创建一个散列对象，将每所学校的 id 存储起来，这样您就可以将学生推送给它：

var hash=x.reduce(function(obj,el){
 (obj[el.school.id]=obj[el.school.id]||{id:el.school.id,name:el.school.name,data:[]}).data.push({name:el.name,age:el.age});
  return obj;
},{});

var arr=Object.values(hash);

http://jsbin.com/vedajijiye/edit?console

【讨论】：

【解决方案5】：

let x = [
    {name: "james", age: 10, school: {id:1, name:"London"}},
    {name: "james_2", age: 11, school: {id:1, name:"London"}},
    {name: "john", age: 12, school: {id:2, name:"India"}},
    {name: "johnny", age: 56, school: {id:3, name:"USA"}}
];

let result = [];
for(var i = 0; i < x.length; i++) {
  var person = x[i];
  var school = result.find(s => s.id === person.school.id);
  if(!school) {
    school = {
      id: person.school.id,
      name: person.school.name,
      data: []
    };
    result.push(school);
  }
  school.data.push(person);
}

console.log(result);

【讨论】：

【解决方案6】：

如果 id 不存在，使用 reduce 并简单地将新对象推送到结果数组中，否则只需更新找到的对象中的数据数组

const myArray = x.reduce((res, data) => {
  const found = res.find(o => o.id === data.school.id);

  if (!found) {
    res.push({
        id: data.school.id,
        name: data.school.name,
        data: [data]
    });
  } else {
    found.data.push(data);
  }
  return res;
}, []);


console.log(myArray)

【讨论】：