I have the following Array

[
  { Month: '2021-05', Count: 36 },
  { Month: '2021-06', Count: 1048 },
  { Month: '2021-07', Count: 572 },
  { Month: '2021-09', Count: 3 },
  { Month: '2021-12', Count: 52 },
  { Month: '2022-01', Count: 4 },
  { Month: '2022-02', Count: 273 },
  { Month: '2022-04', Count: 96 }
]

where I am missing a few months. I know how many months is needed (could be 12 or could be more or less) and I need the missing months (like 2021-08 in this case) to be added with a count of 0. How to go about it?

CodePudding user response：

Here's a pure, functional approach which will create a new array with new items, inserting all of the missing months in order. The code includes some comments explaining the procedure:

const parseDate = str => str.split('-').map(Number);
const formatDate = (year, month) => `${year}-${String(month).padStart(2, '0')}`;

function createContinuousMonthCounts (array) {
  const all = [];
  // get initial year/month values from first item
  let [year, month] = parseDate(array[0].Month);

  const advanceDate = () => {
    month  = 1;
    if (month > 12) {
      year  = 1;
      month = 1;
    }
  };

  for (const item of array) {
    const [y, m] = parseDate(item.Month);
    // while the current month is not equal to the current item's month,
    // create an entry for the month, append it, and advance to the next month
    while (year !== y || month !== m) {
      all.push({Month: formatDate(year, month), Count: 0});
      advanceDate();
    }
    // after we're up to date, add the current item and advance the date
    all.push({...item});
    advanceDate();
  }

  return all;
}

const array = [
  { Month: '2021-05', Count: 36 },
  { Month: '2021-06', Count: 1048 },
  { Month: '2021-07', Count: 572 },
  { Month: '2021-09', Count: 3 },
  { Month: '2021-12', Count: 52 },
  { Month: '2022-01', Count: 4 },
  { Month: '2022-02', Count: 273 },
  { Month: '2022-04', Count: 96 },
];

const all = createContinuousMonthCounts(array);

for (const {Month, Count} of all) console.log(Month, Count);

CodePudding user response：

Just a shot into the dark (please consider adding some Code to your question):

const months = [
  { Month: '2021-05', Count: 36 },
  { Month: '2021-06', Count: 1048 },
  { Month: '2021-07', Count: 572 },
  { Month: '2021-09', Count: 3 },
  { Month: '2021-12', Count: 52 },
  { Month: '2022-01', Count: 4 },
  { Month: '2022-02', Count: 273 },
  { Month: '2022-04', Count: 96 }
];

const neededMonths = [
  "2021-01","2021-02","2021-03","2021-04","2021-05","2021-06","2021-07","2021-08","2021-09","2021-10","2021-11","2021-12"
]

const missedMonths = [];

months.map( m => {
  if(neededMonths.indexOf(m.Month) == -1 ){
    missedMonths.push(m.Month);
  }
});

console.log(missedMonths);

CodePudding user response：

You first need a method to find all the months between a range, then iterate across all the months and add the missing ones with count: 0:

const months = [
  { Month: '2021-05', Count: 36 },
  { Month: '2021-06', Count: 1048 },
  { Month: '2021-07', Count: 572 },
  { Month: '2021-09', Count: 3 },
  { Month: '2021-12', Count: 52 },
  { Month: '2022-01', Count: 4 },
  { Month: '2022-02', Count: 273 },
  { Month: '2022-04', Count: 96 }
]

const firstMonth = months.at(0).Month;
const lastMonth = months.at(-1).Month;

const [initialYear, initialMonth] = firstMonth.split('-');
const [endingYear, endingMonth] = lastMonth.split('-');

const allMonths = [];

let currentMonth = initialMonth;
let currentYear = initialYear;
while (`${currentYear}-${('' currentMonth).padStart(2, '0')}` !== lastMonth) {
  allMonths.push(`${currentYear}-${('' currentMonth).padStart(2, '0')}`);
  currentMonth  ;
  if (currentMonth === 13) {
    currentMonth = 1;
    currentYear  ;
  }
}

allMonths.forEach(month => {
  if (!months.find(m => m.Month === month)) {
     months.push({Month: month, count: 0});
  }
});

console.log(months);

CodePudding user response：

Here is a simple solution:

• Sort the input array by date and iterate
• Insert each item in a new array called result
  • But before inserting, check if last month in result array and current month have gaps; use a nested loop to fill the gap

const array = [
  { Month: "2021-05", Count: 36 },
  { Month: "2021-06", Count: 1048 },
  { Month: "2021-07", Count: 572 },
  { Month: "2021-09", Count: 3 },
  { Month: "2021-12", Count: 52 },
  { Month: "2022-01", Count: 4 },
  { Month: "2022-02", Count: 273 },
  { Month: "2022-04", Count: 96 }
];
let result = [];
array.sort(function(a, b) {
  return a.Month.localeCompare(b.Month);
});
array.forEach(function(item) {
  function addmonth(yymm) {
    let yy = Number(yymm.split("-")[0]);
    let mm = Number(yymm.split("-")[1])   1;
    mm  = 1;
    if (mm > 12) {
      mm = 1;
      yy  = 1;
    }
    return yy.toString()   "-"   mm.toString().padStart(2, "0");
  }
  if (result.length > 0) {
    for (let yymm = addmonth(result[result.length - 1].Month); yymm < item.Month; yymm = addmonth(yymm)) {
      result.push({
        Month: yymm,
        Count: 0
      });
    }
  }
  result.push(item);
});
console.log(result);