Javascript 进行计算和筛选列表

Question

我有以下数组 -

const data=[
{
  month:"nov",
  veryLate:3,
  Late:5,
  onTime:2
},
{
  month:"dec",
  veryLate:1,
  Late:3,
  onTime:16
},
{
  month:"jan",
  veryLate:28,
  Late:1,
  onTime:1
},
}

我想对这个数组进行过滤和计算，以便获得百分比。

例如。 veryLate + Late+ onTime = (3+5+2) = 10

那么百分比是-

const data= [
{
  month:"nov",
  veryLate:30,
  Late:50,
  onTime:20
},
{
  month:"dec",
  veryLate:5,
  Late:15,
  onTime:80
},
,
{
  month:"jan",
  veryLate:98.33,
  Late:3.33,
  onTime:3.33
},]

为了计算这个我在下面执行了，但是在括号上出现语法错误 -

var filteredData=data.map(x=>{
  x.month,
  x.veryLate/(x.veryLate+x.Late+x.onTime)*100,
  x.Late/(x.veryLate+x.Late+x.onTime)*100,
  x.onTime/(x.veryLate+x.Late+x.onTime)*100,
});

如何获得计算结果？

Answer 1

map() 方法需要 return 一个值。

试试这个

var filteredData=data.map(x => {
   // get the original values to avoid repeating x. 
   const {month, veryLate, Late, onTime} = x;
   
   // do your calculations
   const newVeryLate = veryLate / ( veryLate + Late + onTime) * 100;
   const newLate = Late / (veryLate + Late + onTime) * 100;
   const newOnTime = onTime / (veryLate + Late + onTime) * 100;
   
   // return the new object
   return {month, veryLate: newVeryLate, Late: newLate, onTime: newOnTime}
});

Answer 2

x.veryLate 不会在 x 中工作它应该是 veryLate 本身对于其他人来说是一样的

const data=[
{
  month:"nov",
  veryLate:3,
  Late:5,
  onTime:2
},
{
  month:"dec",
  veryLate:1,
  Late:3,
  onTime:16
},
{
  month:"jan",
  veryLate:28,
  Late:1,
  onTime:1
},
]

var filteredData= data.map(x => (
   {
    ...x, 
    veryLate:  x.veryLate/(x.veryLate+x.Late+x.onTime)*100,         
    Late: x.Late/(x.veryLate+x.Late+x.onTime)*100, 
    onTime: x.onTime/(x.veryLate+x.Late+x.onTime)*100
  })
)

console.log(filteredData)

您还必须将返回的对象字面量括在括号中。目前花括号被表示为函数体。

Answer 3

var filteredData=data.reduce((a, v)=>{
  let obj = {};
  let sum = v.veryLate+v.Late+v.onTime;
  obj.month = v.month;
  obj.veryLate = v.veryLate/sum*100;
  obj.Late = v.Late/sum*100;
  obj.onTime = v.onTime/sum*100;
  a.push(obj)
  return a;
}, []);

抛出错误，因为：

数据数组没有右括号
map 方法没有 returning 任何东西。如果你想 return 从中获取一个对象，请使用 return 关键字。

Answer 4

问题是传递给 Array.prototype.map 的回调需要为每次迭代 return 一些东西，而在您当前的实现中，您没有 returning 任何东西。

您可以使用map如下图：

const data = [
  { month: "nov", veryLate: 3, Late: 5, onTime: 2 },
  { month: "dec", veryLate: 1, Late: 3, onTime: 16 },
  { month: "jan", veryLate: 28, Late: 1, onTime: 1 },
];

const filteredData = data.map(({ month, veryLate, Late, onTime }) => {
  const total = veryLate + Late + onTime;
  return {
    month,
    veryLate: (veryLate / total) * 100,
    Late: (Late / total) * 100,
    onTime: (onTime / total) * 100,
  };
});

console.log(filteredData);

如果您发现 map 令人困惑，您也可以使用常规 for 循环来完成，如下所示：

const data = [
  { month: "nov", veryLate: 3, Late: 5, onTime: 2 },
  { month: "dec", veryLate: 1, Late: 3, onTime: 16 },
  { month: "jan", veryLate: 28, Late: 1, onTime: 1 },
];

const filteredData = [];
for (let i = 0; i < data.length; i++) {
  const { month, veryLate, Late, onTime } = data[i];
  const total = veryLate + Late + onTime;
  result.push({
    month,
    veryLate: (veryLate / total) * 100,
    Late: (Late / total) * 100,
    onTime: (onTime / total) * 100,
  });
}

console.log(filteredData);

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