How to fill in missing months of last year in an array using javascript

Question

I have an array of months and its count as follows:

[
            {
                "registered_to_month": "04-2022",
                "count": "3"
            },
            {
                "registered_to_month": "03-2022",
                "count": "4"
            },
            {
                "registered_to_month": "02-2022",
                "count": "6"
            },
            {
                "registered_to_month": "01-2022",
                "count": "6"
            },
            {
                "registered_to_month": "11-2021",
                "count": "11"
            }
        ]

This result I am getting last 12 months The months which is not available I want to replace with 0 so that I can plot in the graph. I am not able to figure out how can I solve this.

Answer 1

We'll first generate an array of dates from the start date to the end date in the given data. Then compare which date exists in the given data. If a date exists in the given data, it is pushed to the result array else a new item is added to the result array with count as 0.

data = [
    {
        "registered_to_month": "04-2022",
        "count": "3"
    },
    {
        "registered_to_month": "03-2022",
        "count": "4"
    },
    {
        "registered_to_month": "02-2022",
        "count": "6"
    },
    {
        "registered_to_month": "01-2022",
        "count": "6"
    },
    {
        "registered_to_month": "11-2021",
        "count": "11"
    }
]

const generateAllDates = (startDate, endDate) =>{
  var dates = [];
  var startDateYr = startDate.split('-')[1];
  var startDateMon = startDate.split('-')[0];
  var endDateYr = endDate.split('-')[1];
  var endDateMon = endDate.split('-')[0];
  
  for(var year = startDateYr; year <= endDateYr; year++) {
      for(var month = startDateMon; month <= 12; month++) {
          dates.push(month.toString().padStart(2, "0")+"-"+year);
          if (year >= endDateYr && month >= endDateMon) break;
      };
      startDateMon = 1;
  };
  return dates.reverse();
}

const fillMissingData = (data) =>{
  // assuming the dates in data are arranged
  // in descending order, sort first if otherwise
  const startDate = data[data.length-1]["registered_to_month"]
  const endDate = data[0]["registered_to_month"]
  const allDates = generateAllDates(startDate, endDate)
  var resultData = []
  
  for (const genDate of allDates){
    let exists = true
    for(const item of data){
      date = item["registered_to_month"]
      if (genDate == date){
        exists = true
        resultData.push(item);
        break
      }else{
        exists = false
      }
    }
    if (!exists){
      resultData.push({"registered_to_month": genDate, "count": '0'})
    } 
  } 
  return resultData;
  return resultData;
}

fillMissingData(data)

Answer 2

You can have an array of 12 elements with all values initially 0 and loop on all values you have. Add count to array as

var counts = new Array(12).fill(0);
var values = JSON.parse(your_string_with_json);
for (var i= 0; i<values.length; i++)
{
  var month = values[i].registered_to_month.split('-')[0];
  counts[parseInt(month)] = values[i].counts;
}
var allvalues;
for(var j= 0; j<counts.length; j++)
{
  var val = {
    registered_to_month: j<10 ? '0' + j : j,
    count: counts[j]
  };
  allvalues.push(val);
}