对象内部对象属性的组合数组，内部数组[重复]

Question

给定这个对象数组：

[
    {"Code": 101, "Description": "Invoice"},
    {"Code": 102, "Description": "Credit"},
    {"Code": 103, "Description": "Credit"},
    {"Code": 111, "Description": "Invoice"},
    {"Code": 112, "Description": "Credit"},
    {"Code": 113, "Description": "Credit"},
    {"Code": 182, "Description": "Backup"}
]

我需要将匹配Descriptions 的对象组合成一个带有Codes 数组的单个对象，如下所示：

[
    {"Code": [101,111], "Description": "Invoice"},
    {"Code": [102,103,112,113], "Description": "Credit"},
    {"Code": [182], "Description": "Backup"}
]

我已尝试使用下面的 groupBy() 辅助函数（香草 JS 函数），但它不起作用，因为我得到了一个带有单个 undefined 属性的 Object，其原始数组的值为：

var groupBy = function (arr, criteria) {
    return arr.reduce(function (obj, item) {

        // Check if the criteria is a function to run on the item or a property of it
        var key = typeof criteria === 'function' ? criteria(item) : item[criteria];

        // If the key doesn't exist yet, create it
        if (!obj.hasOwnProperty(key)) {
            obj[key] = [];
        }

        // Push the value to the object
        obj[key].push(item);

        // Return the object to the next item in the loop
        return obj;

    }, {});
};

var array = [
    {"Code": 101, "Description": "Invoice"},
    {"Code": 102, "Description": "Credit"},
    {"Code": 103, "Description": "Credit"},
    {"Code": 111, "Description": "Invoice"},
    {"Code": 112, "Description": "Credit"},
    {"Code": 113, "Description": "Credit"},
    {"Code": 182, "Description": "Backup"}
];

var groupDescription = groupBy(array, array.forEach(document => document.Description));

console.log(groupDescription);

实现预期输出的最佳方式是什么？

Answer 1

您的预期输出是Array，但groupBy 函数中的reduce 逻辑将Object 作为其初始值。不清楚为什么要为输入数组中的每个项目运行 criteria 函数，因为 Description 是 String，而不是 Array。

一种更简单的方法（可能是最好的，也可能不是）：

• 以数组形式获取唯一的 Descriptions 集
• 迭代该数组并针对每个Description，过滤原始数组并获得Codes

见下文：

var arr = [
  {"Code": 101, "Description": "Invoice"},
  {"Code": 102, "Description": "Credit"},
  {"Code": 103, "Description": "Credit"},
  {"Code": 111, "Description": "Invoice"},
  {"Code": 112, "Description": "Credit"},
  {"Code": 113, "Description": "Credit"},
  {"Code": 182, "Description": "Backup"}
];

// expected output
//[
//  {"Code": [101,111], "Description": "Invoice"},
//  {"Code": [102,103,112,113], "Description": "Credit"},
//  {"Code": [182], "Description": "Backup"}
//]

var grouped = Array
  .from(new Set(arr.map(o => o.Description))) // get unique Descriptions as array
  .map(d => { // iterate that array
    return {
      "Code": arr
        .filter(o => o.Description === d) 
        .map(o => o.Code), // return just the Code for original array items matching this unique Description
      "Description": d  // the Description
    }
  });
  
console.log(grouped);