使用javascript中的值数组过滤深度嵌套的对象数组

我想知道如何用javascript中的值数组过滤深度嵌套的对象数组（动态） 注意，

Obj

是动态的

var result = getData(obj);
getData(obj){
  var getcn = obj.map(e=>e.cn);
  var tot = obj.filter(e=>getcn.includes(e.cn));
}

预期产出：

[{
  "cn": "SG",
  "total": 2 // length of cn `SG`
},{
  "cn": "MY",
  "total": 1
},{
  "cn": "TH",
  "total": 1
}]

var obj=[{cn:“SG”，amt:“30”}，{cn:“SG”，amt:“40”}，{cn:“MY”，amt:“100”}，{cn:“TH”，amt:“40”}]；
让res=对象减少（（acc，cur）=>{
if（acc.some（obj=>obj.cn==cur.cn））{
返回acc.map（obj=>obj.cn===cur.cn？{cn:obj.cn，total:obj.total+1}:obj）
}
返回acc.concat（{cn:cur.cn，总计：1}）
},[])
console.log（res）

var obj=[
{
“cn”：“SG”，
“金额”：“30”
},
{
“cn”：“SG”，
“金额”：“40”
},
{
“cn”：“我的”，
“金额”：“100”
},
{
“cn”：“TH”，
“金额”：“40”
}
]
函数getData（obj）{
设频率={}，结果=[]；
对象映射（（项目）=>{
如果（item.cn频率）
频率[item.cn]++；
其他的
频率[item.cn]=1；
})
for（让对象的[键，值]输入（频率））
push（{cn:key，total:value}）
返回结果；
}
log（getData（obj））

我不确定“obj是动态的”是什么意思，但基本上，您需要遍历一个值数组，并将每个值添加到一个新数组中。但是，如果该值已经存在于这个新数组中，则只需将其总数增加1

//input
var input = [{
  "cn": "SG",
  "amt": "30"
},{
  "cn": "SG",
  "amt": "40"
},{
  "cn": "MY",
  "amt": "100"
},{
  "cn": "TH",
  "amt": "40"
}];

const getData = (data) => {
  const entryIndexByCn = {}; // store index of the value in the new array, 
                             // so we could then increase total by 1
                             // in case the value was already added

  return data.reduce((memo, entry) => {
    // get index of the value in the new array
    const entryIndex = entryIndexByCn[entry.cn];

    // if value is in the new array, increase total by 1
    if (entryIndex !== undefined) {
      memo[entryIndex].total += 1;
    } else { 
      // if not, record index of the value to
      // address it later if we meet the value again
      // to be able to increase its total
      entryIndexByCn[entry.cn] = memo.length;

      // and add new value to the new array
      memo.push({
        cn: entry.cn,
        total: 1
      });
    }

    return memo;
  }, []);
}

//input
var input = [{
  "cn": "SG",
  "amt": "30"
},{
  "cn": "SG",
  "amt": "40"
},{
  "cn": "MY",
  "amt": "100"
},{
  "cn": "TH",
  "amt": "40"
}];

const getData = (data) => {
  const entryIndexByCn = {}; // store index of the value in the new array, 
                             // so we could then increase total by 1
                             // in case the value was already added

  return data.reduce((memo, entry) => {
    // get index of the value in the new array
    const entryIndex = entryIndexByCn[entry.cn];

    // if value is in the new array, increase total by 1
    if (entryIndex !== undefined) {
      memo[entryIndex].total += 1;
    } else { 
      // if not, record index of the value to
      // address it later if we meet the value again
      // to be able to increase its total
      entryIndexByCn[entry.cn] = memo.length;

      // and add new value to the new array
      memo.push({
        cn: entry.cn,
        total: 1
      });
    }

    return memo;
  }, []);
}