vaadin-date-picker-helper.html

<script>
  window.vaadin = window.vaadin || {};
  vaadin.elements = vaadin.elements || {};
  vaadin.elements.datepicker = vaadin.elements.datepicker || {};

  vaadin.elements.datepicker.DatePickerHelper = {
    /**
     * Get ISO 8601 week number for the given date.
     *
     * @param {Date} Date object
     * @return {Number} Week number
     */
    _getISOWeekNumber: function(date) {
      // Ported from Vaadin Framework method com.vaadin.client.DateTimeService.getISOWeekNumber(date)
      var dayOfWeek = date.getDay(); // 0 == sunday

      // ISO 8601 use weeks that start on monday so we use
      // mon=1,tue=2,...sun=7;
      if (dayOfWeek === 0) {
        dayOfWeek = 7;
      }
      // Find nearest thursday (defines the week in ISO 8601). The week number
      // for the nearest thursday is the same as for the target date.
      var nearestThursdayDiff = 4 - dayOfWeek; // 4 is thursday
      var nearestThursday = new Date(date.getTime() + nearestThursdayDiff * 24 * 3600 * 1000);

      var firstOfJanuary = new Date(0, 0);
      firstOfJanuary.setFullYear(nearestThursday.getFullYear());

      var timeDiff = nearestThursday.getTime() - firstOfJanuary.getTime();

      // Rounding the result, as the division doesn't result in an integer
      // when the given date is inside daylight saving time period.
      var daysSinceFirstOfJanuary = Math.round(timeDiff / (24 * 3600 * 1000));

      return Math.floor((daysSinceFirstOfJanuary) / 7 + 1);
    },

    /**
     * Check if two dates are equal.
     *
     * @param {Date} date1
     * @param {Date} date2
     * @return {Boolean} True if the given date objects refer to the same date
     */
    _dateEquals: function(date1, date2) {
      if (date1 && date2) {
        return date1.getFullYear() === date2.getFullYear() &&
          date1.getMonth() === date2.getMonth() &&
          date1.getDate() === date2.getDate();
      } else {
        return false;
      }
    },

    /**
     * Check if the given date is in the range of allowed dates.
     *
     * @param {Date} date The date to check
     * @param {Date} min Range start
     * @param {Date} max Range end
     * @return {Boolean} True if the date is in the range
     */
    _dateAllowed: function(date, min, max) {
      return (!min || date >= min) && (!max || date <= max);
    },

    /**
     * Get closest date from array of dates.
     *
     * @param {Date} date The date to compare dates with
     * @param {Array} dates Array of date objects
     * @return {Date} Closest date
     */
    _getClosestDate: function(date, dates) {
      return dates.filter(function(date) {
        return date !== undefined;
      })
       .reduce(function(closestDate, candidate) {
         if (!candidate) {
           return closestDate;
         }

         if (!closestDate) {
           return candidate;
         }

         var candidateDiff = Math.abs(date.getTime() - candidate.getTime());
         var closestDateDiff = Math.abs(closestDate.getTime() - date.getTime());
         return candidateDiff < closestDateDiff ? candidate : closestDate;
       });
    }
  };
</script>