基于唯一值计数的 JS 对象过滤器答案

【问题标题】：JS Object filter based on count of unique values基于唯一值计数的 JS 对象过滤器
【发布时间】：2022-01-22 17:03:35
【问题描述】：

考虑以下示例 JS 对象

const samplejson = [
    {id:'1',value: "AC",},
    {id:'2',value: "AB",},
    {id:'3',value: "AC",},
    {id:'4',value: "AA",},
    {id:'5',value: "AA",},
    {id:'6',value: "AA",},
    {id:'7',value: "AB",},
    {id:'8',value: "AC",},
    {id:'9',value: "AA",},
    {id:'10',value: "AA",},
]

我想根据值的唯一计数和降序过滤 JS 对象，如下所示

基于值计数 AA - 5、AB - 2 和 AC - 3，但我需要输出为 AA,AC

在 react 或 JS 中如何实现呢？

【问题讨论】：

请注意不是 JSON，而是一个 JS 对象。我已经编辑了问题以反映这一点

标签： javascript arrays reactjs object

【解决方案1】：

您可以通过以下步骤找到您想要的结果：

统计数值。
按值/计数对的计数降序排列。
删除计数，只保留值。

const items = [
  { id:  '1', value: "AC" },
  { id:  '2', value: "AB" },
  { id:  '3', value: "AC" },
  { id:  '4', value: "AA" },
  { id:  '5', value: "AA" },
  { id:  '6', value: "AA" },
  { id:  '7', value: "AB" },
  { id:  '8', value: "AC" },
  { id:  '9', value: "AA" },
  { id: '10', value: "AA" },
];

const tally = new Map();
for (const { value } of items) {
  if (!tally.has(value)) tally.set(value, 0);
  tally.set(value, tally.get(value) + 1);
}

// displaying as object because Map instances show empty in the snippet log
console.log(Object.fromEntries(tally));

const results = Array.from(tally)
  .sort(([,countA], [,countB]) => countB - countA)
  .map(([value]) => value);

console.log(results);

【讨论】：

【解决方案2】：

看看这个：

const data = [{id:'1',value: "AC",},{id:'2',value: "AB",},{id:'3',value: "AC",},    {id:'4',value: "AA",},{id:'5',value: "AA",},{id:'6',value: "AA",},{id:'7',value: "AB",},    {id:'8',value: "AC",},{id:'9',value: "AA",},{id:'10',value: "AA",},];

const result = Object.entries(
  data.reduce((acc, { value }) => ({ ...acc, [value]: (acc[value] || 0) + 1 }), {})
).sort((a1, a2) => a2[1] - a1[1])
.map(([key]) => key)
.join(',');

console.log(result);

【讨论】：

【解决方案3】：

您可以遍历示例数据中的任何键并计算字典中值的每次出现。然后，您既可以打印字典以获取出现次数的列表，也可以仅打印一个值的出现次数。

const data = [
    {id:'1',value: "AC",},
    {id:'2',value: "AB",},
    {id:'3',value: "AC",},
    {id:'4',value: "AA",},
    {id:'5',value: "AA",},
    {id:'6',value: "AA",},
    {id:'7',value: "AB",},
    {id:'8',value: "AC",},
    {id:'9',value: "AA",},
    {id:'10',value: "AA",},
]


// make a dict to store and count occurrences
dict = {};

//iterate over every key in your data and keep count in dict
//(initializing it to 1 if it not exists yet)
for(let i = 0; i < data.length; i++){
  value = data[i].value;
  if(value in dict){
    dict[value]++;
  }else{
    dict[value] = 1;
  }
}

// here the amount of occurrences are know
console.log(dict);
amountOfAA = dict['AA'];

输出： { AC：3，AB：2，AA：5} 5

【讨论】：