如何使用一个重复键和另一个唯一键过滤一组对象[重复]答案

【问题标题】：How can I filter an array of objects with one duplicate key and another unique key [duplicate]如何使用一个重复键和另一个唯一键过滤一组对象[重复]
【发布时间】：2021-03-31 00:31:09
【问题描述】：

我有一个对象数组，比如

const data = [
{date: "2020-12-21", time: "09:10:00"},
{date: "2020-12-21", time: "09:20:00"},
{date: "2020-12-21", time: "09:30:00"},
{date: "2020-12-22", time: "12:50:00"},
{date: "2020-12-22", time: "13:00:00"},
{date: "2020-12-22", time: "13:10:00"},
{date: "2020-12-22", time: "13:20:00"},
{date: "2020-12-23", time: "10:40:00"},
{date: "2020-12-23", time: "10:50:00"},
{date: "2020-12-23", time: "11:00:00"},

]

我正在尝试使用 javascript 获得以下过滤结果。有人可以帮我吗？

data = [
    {date: "2020-12-21", time: ["09:10:00", "09:20:00","09:30:00" ]},
    {date: "2020-12-22", time: ["12:50:00", "13:00:00","13:10:00" ]},
    {date: "2020-12-23", time: ["10:40:00","10:50:00","11:00:00" ]},
    ]

【问题讨论】：

标签： javascript arrays json object filter

【解决方案1】：

const data = [
  {date: "2020-12-21", time: "09:10:00"},
  {date: "2020-12-21", time: "09:20:00"},
  {date: "2020-12-21", time: "09:30:00"},
  {date: "2020-12-22", time: "12:50:00"},
  {date: "2020-12-22", time: "13:00:00"},
  {date: "2020-12-22", time: "13:10:00"},
  {date: "2020-12-22", time: "13:20:00"},
  {date: "2020-12-23", time: "10:40:00"},
  {date: "2020-12-23", time: "10:50:00"},
  {date: "2020-12-23", time: "11:00:00"},
]

const output = data.reduce((acc, cur) => {
  if (!acc[cur.date]) acc[cur.date] = {
    date: cur.date,
    time: []
  };
  acc[cur.date].time.push(cur.time);
  return acc;
}, {});

const result = Object.values(output)

console.log(result);

【讨论】：

【解决方案2】：

你可以使用reduce来实现，

const data = [
{date: "2020-12-21", time: "09:10:00"},
{date: "2020-12-21", time: "09:20:00"},
{date: "2020-12-21", time: "09:30:00"},
{date: "2020-12-22", time: "12:50:00"},
{date: "2020-12-22", time: "13:00:00"},
{date: "2020-12-22", time: "13:10:00"},
{date: "2020-12-22", time: "13:20:00"},
{date: "2020-12-23", time: "10:40:00"},
{date: "2020-12-23", time: "10:50:00"},
{date: "2020-12-23", time: "11:00:00"},

]

let res = data.reduce((acc, curr) => {
  let index = acc.findIndex(item => item.date === curr.date);
  if(index > -1) {
    acc[index].time.push(curr.time);
  }
  else acc.push({date: curr.date, time: [curr.time]});
  return acc;
}, [])

console.log(res);

【讨论】：

findIndex inside reduce() 方法在循环内发生循环，因此o-notation 性能将是O(n*n)。最好不要在 reduce 中使用 findIndex。
这行得通。谢谢。