compare dates

by aaronk85

HTML

<input type="text" name="firstname" id="firstname" placeholder="first name" value="">
<input type="text" name="nextdate" id="nextdate" value="2014-02-11">
<input type="text" name="lastdate" id="lastdate" value="2014-02-05">
<input type="text" name="diffdays" id="diffdays" placeholder="diffdays - 1" value="">

JavaScript

$('#firstname').on('input', function () {

    var lastdate = $('#lastdate').val();
    var nextdate = $('#nextdate').val();
    var extraday = -1;

    var oneDay = 24 * 60 * 60 * 1000; // hours*minutes*seconds*milliseconds

    var firstDate = lastdate;
    var firstDateFormatted = firstDate.replace("-", ",");
    firstDate = new Date(firstDateFormatted);

    var secondDate = nextdate;
    var secondDateFormatted = secondDate.replace("-", ",");
    secondDate = new Date(secondDateFormatted);

    var diffDays = (Math.round(Math.abs((firstDate.getTime() - secondDate.getTime()) / (oneDay)))) + extraday;
    $('#diffdays').val((diffDays));
});