Weeks in month using Moment.js

weeks_in_month.js

var get_calendar;
var calendar, endDay, firstDay, firstWeekDay, headerRow, i, j, lastWeekDay, len, len1, month, monthRange, row, startDate, week, weekRange, weeks, year,
  indexOf = [].indexOf || function(item) { for (var i = 0, l = this.length; i < l; i++) { if (i in this && this[i] === item) return i; } return -1; };

get_calendar = function(year, month) {
  startDate = moment([year, month]);
  firstDay = moment(startDate).startOf('month');
  endDay = moment(startDate).endOf('month');
  monthRange = moment.range(firstDay, endDay);
  weeks = [];
  monthRange.by('days', function(moment) {
    var ref;
    ref = void 0;
    if (ref = moment.week()) {
      indexOf.call(weeks, ref) < 0;
      return weeks.push(moment.week());
    }
  });
  calendar = [];
  i = 0;
  len = weeks.length;
  while (i < len) {
    week = weeks[i];
    if (i > 0 && week < weeks[i - 1]) {
      firstWeekDay = moment([year, month]).add(1, 'year').week(week).day(1);
      lastWeekDay = moment([year, month]).add(1, 'year').week(week).day(7);
    } else {
      firstWeekDay = moment([year, month]).week(week).day(1);
      lastWeekDay = moment([year, month]).week(week).day(7);
    }
    weekRange = moment.range(firstWeekDay, lastWeekDay);
    calendar.push(weekRange);
    i++;
  }
  return calendar;
};

The jsFiddle doesn't seem to be working. Chrome 68