Javascript make calculations and filter list-CodePudding

I have below array -

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
},
}

I want to filter and make calculations on this array such that percentage can be obtained.

Eg. veryLate Late onTime = (3 5 2) = 10

So percentage wise it is -

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
},]

To calculate this I had performed below , but getting syntax error over brackets -

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,
});

How can I obtained calculated results?

CodePudding user response：

x.veryLate wont work in x it should be veryLate itself same for the others

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)

You also must wrap the returning object literal into parentheses. Currently the curly braces is being denoted as the function body.

CodePudding user response：

The map() method needs to return a value.

Try this

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}
});

CodePudding user response：

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;
}, []);

Throwing error because:

The data array has no closing bracket
map method is not returning anything. if you want to return an object from it use return keyword.

CodePudding user response：

The problem is that the callback passed to Array.prototype.map needs to return something for every iteration and in your current implementation you aren't returning anything.

You can use map as shown below:

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);

If you're finding map confusing, you can also do it with a regular for loop, as shown below:

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);

Additional Documentation:

Object Destructuring