Find all missing dates in an JSON object in Javascript / Typescript

Question

In my application I am in need to show missing date range. I tried to get the first and last date but got struck to proceed further. when I tried, I got only the first missing date but the expected output is to display all missing dates from the start date to end date.

https://jsfiddle.net/bgef59x2/3/

https://stackblitz.com/edit/ionic-rknmsc?file=pages%2Fhome%2Fhome.ts

var data={
"dataObj"=[
{"custom_date":"2020-04-13"},
{"custom_date":"2020-04-19"},
{"custom_date":"2020-04-20"},
{"custom_date":"2020-04-21"}
]}

my startDate would be "2020-04-13" and enddate would be "2020-04-21" Expected output:

const result =["2020-04-14","2020-04-15","2020-04-16","2020-04-17","2020-04-18"]

Guide me to achieve the expected result in JavaScript/ Typescript. I have not included momentJs in my application.

What do you mean by missing? Are they undefined, null, empty strings? I reviewed the link you added, in which file is the problem? Can you update your original answer with more detail about the exact problem you have, what you've tried and why that hasn't worked so far? — Isolated
– Isolated, Commented May 11, 2020 at 17:35
Create an array and fill it with all dates between 'start' and 'end' date. Then, remove dates in your dataObj by splic() — Jack Ting
– Jack Ting, Commented May 11, 2020 at 17:51
Are all your dates in order? Or do they need to be sorted first? Are you looking to fill only the missing dates? — Isolated
– Isolated, Commented May 11, 2020 at 17:52

Eliseo · Accepted Answer · 2020-05-11 18:16:51Z

1

Web, just only create a llop from date to date, check if is in the array a push in an array

missingDates:string[]=[]
const missingDates: string[] = [];

const from = new Date(this.data[0].custom_date);
const to = new Date(this.data[this.data.length - 1].custom_date);
for (let fecha = from;fecha < to;fecha = new Date(fecha.getTime() + 24 * 60 * 60 * 1000)) {
  const date =fecha.getFullYear() +"-" +
    ("00" + (fecha.getMonth() + 1)).slice(-2) +"-" +
    ("00" + fecha.getDate()).slice(-2);

  if (!this.data.find(x => x.custom_date == date)) missingDates.push(date);
}
console.log(missingDates)

answered May 11, 2020 at 18:16

Eliseo

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Comments

wawan · Accepted Answer · 2020-05-11 18:40:36Z

Better solution exists, but this script excludes dates as expected :

var dataObj = [
{"custom_date":"2020-04-13"},
{"custom_date":"2020-04-19"},
{"custom_date":"2020-04-20"},
{"custom_date":"2020-04-21"}
];
var dates = dataObj.map(d => d.custom_date)

console.log(getMissingDates(dates));

function getMissingDates(dates) {
  
  var datesParsed= dates.map(d => new Date(d)).sort()
  var allExpectedDates = [];
  var missingDates = [];
  var from = datesParsed[0];
  var to = datesParsed[datesParsed.length - 1];
  var current = from;
  while (current <= to) {
    allExpectedDates.push(formatDate(current));
    current.setDate(current.getDate() + 1);
  }

  return allExpectedDates.filter(el => {
    return dates.indexOf(el) === -1;
  });
}

// from https://stackoverflow.com/questions/23593052/format-javascript-date-as-yyyy-mm-dd :
function formatDate(date) {
    var d = new Date(date),
        month = '' + (d.getMonth() + 1),
        day = '' + d.getDate(),
        year = d.getFullYear();

    if (month.length < 2) 
        month = '0' + month;
    if (day.length < 2) 
        day = '0' + day;

    return [year, month, day].join('-');
}

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