Question 407098 in Javascript Question posted in
A very good W3school tutorial can be found here.

How to fill missing months with 0 values for given years in javascript?

data:

const data = [
  {time: "2020-10-13", value: 3},   
  {time: "2020-11-13", value: 30},  
  {time: "2021-01-13", value: 12}, 
  {time: "2021-02-13", value: 1},   
  {time: "2021-03-13", value: 23},   
  {time: "2021-04-13", value: 10}, ...
]

Im formating this data to this format: [number, number, number][] –> [month, year, value]

For the example data it would be:

[[11, 2020, 3], [10, 2020, 30], [1, 2021, 12], [2, 2021, 1], ...]

How can I add value 0 and month, when the month is missing? So in example, there is 10 months missing in 2020 and 9 months missing in 2021. I would like to add it so it looks like this:

[[1, 2020, 0], [2, 2020, 0],[3, 2020, 0], [4 2020, 0],[5, 2020, 30, [6, 2020, 0],[7, 2020, 0],[8, 2020, 0],[9, 2020, 0], [10, 2020, 30],[11, 2020, 3], [10, 2020, 30], [1, 2021, 12], [2, 2021, 1], ...]

What would be the best way to do it?

Thanks!!

EDIT:

some code I tried:

const months =[1,2,3,4,5,6,7,8,9,10,11,12];
const res = data.flatMap(({time,value}) => {
  const [y,m,d] = time.split("-").map(Number); 
  const res = months.map((month, i) => {
    if (m === month) {
      return [m, y, value]
    } else {
      return [month, y, 0]
    }
  })
  return res;
})

const changeData = (data) => {
    let res = {};
     data.forEach((item) => {
       const {time, value} = item;
       const [y,m,d] = time.split("-").map(Number);
       res[y] !== undefined ? res[y].push({m, value})
       : res[y] = [{m, value}];
    })
    return res;
}
const newData = changeData(data);
console.log(newData)
const months =[1,2,3,4,5,6,7,8,9,10,11,12];

const formatData = () => {
    let result = [];
    for (const [key, value] of Object.entries(newData)) {
        value.slice(0, 12).map((val, i) => {
            const y = key;
            const {m, value} = val;
            const res = months.map((month, i) => {
    
            if (m === month) {
                result.push([m, y, value]);
            } else {
              result.push([month, y, 0]);
            }
        })
        })     
    }
    return result;
}
Tags:

2

Answers


  1. 0

    You should be looping over the time range, not the entries in the newData dictionary. For each month, check if it appears in newData. Use that value if it exists, otherwise default to 0.

    const changeData = (data) => {
  let res = {};
    data.forEach((item) => {
      const {time, value} = item;
      const [y,m,d] = time.split("-").map(Number);
      if (!res[y]) {
        res[y] = {};
      }
      res[y][m] = item;
    })
    return res;
}
const newData = changeData(data);

const formatData = () => {
  let result = [];
  for (let year = 2020; year <= 2021; year++) {
    for (let month = 1; month <= 12; month++) {
      result.push([year, month, newData?.[year]?.[month]?.value || 0]);
    }
  }
  return result;
}
console.log(formatData());
    <script>
const data = [
  {time: "2020-10-13", value: 3},   
  {time: "2020-11-13", value: 30},  
  {time: "2021-01-13", value: 12}, 
  {time: "2021-02-13", value: 1},   
  {time: "2021-03-13", value: 23},   
  {time: "2021-04-13", value: 10}
]
</script>
    Login or Signup to reply.
  2. 0

    This can be done using reduce(). Create all months for years first, then add value to them:

    const data = [
  {time: "2020-10-13", value: 3},
  {time: "2020-11-13", value: 30},
  {time: "2021-01-13", value: 12},
  {time: "2021-02-13", value: 1},
  {time: "2021-03-13", value: 23},
  {time: "2021-04-13", value: 10},
]

const output = data.reduce((accumulator, current) => {
  if (!accumulator.length) {
    const years = Array.from(new Set(data.map(item => Number(item.time.split('-')[0]))));
    years.forEach(el => {
      for (let i = 1; i <= 12; i++) {
        accumulator.push([i, el, 0]);
      }
    });
  }
  const [year, month] = current.time.split('-');
  const el = accumulator.find(
    o => o[0] === parseInt(month, 10) && o[1] === Number(year),
  );
  if (el) {
    el[2] += current.value;
  }
  return accumulator;
}, []);

console.log(output);
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