Moment.js - two dates difference in number of days

I get incorrect results when trying to find numeric difference between two dates:

var startDate = moment( $('[name="date-start"]').val(), "DD.MM.YYYY"), // $('[name="date-start"]').val() === "13.04.2016"
endDate       = moment( $('[name="date-end"]'  ).val(), "DD.MM.YYYY"); // $('[name="date-end"]').val() === "28.04.2016"

var diff = startDate.diff(endDate);

console.log( moment(diff).format('E') );

Between 13.04.2016 and 28.04.2016 I shouldn't get that difference is 3 or 2 days...

I've tried to multiple combinations:

• swap startDate.diff(endDate) with endDate.diff(startDate)
• format('E') with something I've come up searching the SO

result: all the time I get that difference is 3 or 2 days.

What am I doing wrong? Thanks in advance.

From the moment.js docs: format('E') stands for day of week. thus your diff is being computed on which day of the week, which has to be between 1 and 7.

From the moment.js docs again, here is what they suggest:

var a = moment([2007, 0, 29]);
var b = moment([2007, 0, 28]);
a.diff(b, 'days') // 1

Here is a JSFiddle for your particular case:

$('#test').click(function() {
  var startDate = moment("13.04.2016", "DD.MM.YYYY");
  var endDate = moment("28.04.2016", "DD.MM.YYYY");

  var result = 'Diff: ' + endDate.diff(startDate, 'days');

  $('#result').html(result);
});

#test {
  width: 100px;
  height: 100px;
  background: #ffb;
  padding: 10px;
  border: 2px solid #999;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.12.0/moment.js"></script>

<div id='test'>Click Me!!!</div>
<div id='result'></div>

Here's how you can get the comprehensive full fledge difference of two dates.

 function diffYMDHMS(date1, date2) {

    let years = date1.diff(date2, 'year');
    date2.add(years, 'years');

    let months = date1.diff(date2, 'months');
    date2.add(months, 'months');

    let days = date1.diff(date2, 'days');
    date2.add(days, 'days');

    let hours = date1.diff(date2, 'hours');
    date2.add(hours, 'hours');

    let minutes = date1.diff(date2, 'minutes');
    date2.add(minutes, 'minutes');

    let seconds = date1.diff(date2, 'seconds');
    
    console.log(years + ' years ' + months + ' months ' + days + ' days ' + hours + ' 
    hours ' + minutes + ' minutes ' + seconds + ' seconds'); 

    return { years, months, days, hours, minutes, seconds};
}

the diff method returns the difference in milliseconds. Instantiating moment(diff) isn't meaningful.

You can define a variable :

var dayInMilliseconds = 1000 * 60 * 60 * 24;

and then use it like so :

diff / dayInMilliseconds // --> 15

Edit

actually, this is built into the diff method, dubes' answer is better

const FindDate = (date, allDate) => {
        
    // moment().diff only works on moment(). Make sure both date and elements in allDate array are in moment format
    let nearestDate = -1; 
    
    allDate.some(d => {
        const currentDate = moment(d)
        const difference = currentDate.diff(d); // Or d.diff(date) depending on what you're trying to find
        if(difference >= 0){
            nearestDate = d
        }
    });
    
    console.log(nearestDate)
}