Find missing day from array of dates javascript

Question

I am getting an array of day dates from an API:

0:{date: "2016-11-17T00:00:00",…}
1:{date: "2016-11-18T00:00:00",…}
2:{date: "2016-11-19T00:00:00",…}
3:{date: "2016-11-21T00:00:00",…}
4:{date: "2016-11-22T00:00:00",…}
5:{date: "2016-11-23T00:00:00",…}

In this example the array is missing this date:

{date: "2016-11-20T00:00:00",…}

What is the best way to find a missing day from an array of dates in Javascript or Angular?

So that I later would be able to pass it to a datepicker as a disabled day.

I am in the process of thinking about it: Using two for loops — Alessandro Santamaria
– Alessandro Santamaria, Commented Nov 17, 2016 at 12:22

kukkuz · Accepted Answer · 2016-11-17 12:43:59Z

2

Check this out:

First you can sort the array (in case it is not so) using Array.prototype.sort
Then use Array.prototype.reduce and a hash table to find the missing dates

Demo given in snippet below:

var array=[
  {date:"2016-11-17T00:00:00"},
  {date:"2016-11-19T00:00:00"},
  {date:"2016-11-18T00:00:00"},
  {date:"2016-11-21T00:00:00"},
  {date:"2016-11-22T00:00:00"},
  {date:"2016-11-23T00:00:00"},
  {date:"2016-11-27T00:00:00"}
];

var result = array.sort(function(a,b){
   return Date.parse(a.date) - Date.parse(b.date);
}).reduce(function(hash){
  return function(p,c){
    var missingDaysNo = (Date.parse(c.date) - hash.prev) / (1000 * 3600 * 24);
    if(hash.prev && missingDaysNo > 1) {
      for(var i=1;i<missingDaysNo;i++)
        p.push(new Date(hash.prev+i*(1000 * 3600 * 24)));
    }
    hash.prev = Date.parse(c.date);
    return p;
  };
}(Object.create(null)),[]);

console.log(result);

.as-console-wrapper{top:0;max-height:100%!important;}

answered Nov 17, 2016 at 12:43

kukkuz

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1 Comment

kukkuz Over a year ago

@alereisan let me know your thoughts on this... This works if the dates are not in order and also if more than one date is skipped... Note that if more than one days are skipped in succession, that will be handled too...

Dylan Slabbinck · Accepted Answer · 2016-11-17 12:35:21Z

1

Create a new array missingDates[]

Iterate over the array (from your API) using a for loop

for (i = 0; i < array.length; i++){
    var date1 = convert your array item (with index i) to a date
    var date2 = convert your array item (with index i + 1) to a date (keep in mind, index i + 1 cant be > than array.length)

    //calculate diffDays between the 2 dates, if diff is > 1, you have a missing date
    var missingDate = create your missing date (use your date1 variable + 1Day)

    //add misingDate to missingDates[] array
    missingDates.push(missingDate)
}

edited Nov 17, 2016 at 12:35

answered Nov 17, 2016 at 12:28

Dylan Slabbinck

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Comments

Yosvel Quintero · Accepted Answer · 2016-11-17 13:41:54Z

You can do a method getMissingDate to return null if there is not missing date or return the Date object if there is a difference between to dates bigger than one day:

var arr1 = [{date: "2016-11-17T00:00:00"}, {date: "2016-11-18T00:00:00"}, {date: "2016-11-19T00:00:00"}, {date: "2016-11-21T00:00:00"}, {date: "2016-11-22T00:00:00"}, {date: "2016-11-23T00:00:00"}],
    arr2 = [{date: "2016-11-17T00:00:00"}, {date: "2016-11-18T00:00:00"}, {date: "2016-11-19T00:00:00"}, {date: "2016-11-20T00:00:00"}, {date: "2016-11-21T00:00:00"}, {date: "2016-11-22T00:00:00"}, {date: "2016-11-23T00:00:00"}],
    getMissingDate = function(arr) {
      var result = null;
      for (var i = 0, l = arr.length - 1; i < l; i++) {
        var current = new Date(arr[i].date),
            next = new Date(arr[i + 1].date);

        if (1 < Math.ceil(Math.abs(next.getTime() - current.getTime()) / (1000 * 3600 * 24))) {
          result = new Date(current.setDate(current.getDate() + 1));
          break;
        } 
      }

      return result;
    };

console.log('arr1:', getMissingDate(arr1));
console.log('arr2:', getMissingDate(arr2));

user3674768 · Accepted Answer · 2022-05-03 05:05:41Z

0

var array=[
  {date:"2016-01-01T00:00:00"},
  {date:"2016-03-01T00:00:00"},
  {date:"2016-04-01T00:00:00"},
  {date:"2016-07-01T00:00:00"},
  {date:"2016-09-01T00:00:00"},
  {date:"2016-11-01T00:00:00"},
  {date:"2016-12-01T00:00:00"}
];

var result = array.sort(function(a,b){
   return Date.parse(a.date) - Date.parse(b.date);
}).reduce(function(hash){
  return function(p,c){
    var missingMonthsNo= (Date.parse(c.date) - hash.prev) / (1000 * 3600 * 24);
    if(hash.prev && missingMonthsNo> 1) {
      for(var i=1;i<missingMonthsNo;i++)
        p.push(new Date(hash.prev+i*(1000 * 3600 * 24)));
    }
    hash.prev = Date.parse(c.date);
    return p;
  };
}(Object.create(null)),[]);

console.log(result);

.as-console-wrapper{top:0;max-height:100%!important;}

answered May 3, 2022 at 5:05

user3674768

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1 Comment

Amit Over a year ago

As it’s currently written, your answer is unclear. Please edit to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers in the help center.

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