javascript - 寻找一种方法来比较和计算数组中所有嵌套对象键/值对

Question

我有一个对象数组，例如:

const arr1 = [
 {"from":"Monica","to":"Rachel"},
 {"from":"Monica","to":"Rachel"},
 {"from":"Monica","to":"Chandler"},
 {"from":"Monica","to":"Chandler"},
 {"from":"Ross","to":"Chandler"},
 {"from":"Ross","to":"Monica"},
];

我想对两个键(“from”和“to”)相同的所有唯一实例进行排序和计数。

我可以成功地计算出仅比较一个键(“从”或“到”)的每个案例，但我找不到如何比较两者的解决方案。

这是我的示例代码:

let arr2 = Object.values(arr1.reduce((c, { from, to }) => {
 c[from] = c[from] || { from, to, count: 0 };
 c[from].count++;
 return c;
}, {}));
console.log(arr2);

这是我现在得到的结果(因为代码仅比较“from”键):

console.log(arr2);
// Array(2)
// 0: {from: "Monica", to: "Rachel", count: 4}
// 1: {from: "Ross", to: "Chandler", count: 2}
// length: 2

这是我想要实现的结果:

console.log(arr2);
// Array(2)
// 0: {from: "Monica", to: "Rachel", count: 2}
// 1: {from: "Monica", to: "Chandler", count: 2}
// 2: {from: "Ross", to: "Chandler", count: 1}
// 3: {from: "Ross", to: "Monica", count: 1}
// length: 4

Answer 1

• 使用 Array.reduce，您可以通过 from 和 to 变量对键对输入数组进行分组。
• 对于重复项，计数会增加，最后结果将存储在 groupedBy 对象上每个键的值上。
• 您只能使用 Object.values 提取值。

const arr1 = [
 {"from":"Monica","to":"Rachel"},
 {"from":"Monica","to":"Rachel"},
 {"from":"Monica","to":"Chandler"},
 {"from":"Monica","to":"Chandler"},
 {"from":"Ross","to":"Chandler"},
 {"from":"Ross","to":"Monica"},
];

const groupedBy = arr1.reduce((acc, cur) => {
  const key = `${cur.from}_${cur.to}`;
  acc[key] ? acc[key].count ++ : acc[key] = {
    ...cur,
    count: 1
  };
  return acc;
}, {});
const result = Object.values(groupedBy);
console.log(result);