Control for Birthdate with Date.js

Birthdate.js

//reference Date.js
if (!Utilities) var Utilities = {};
$.extend(Utilities,
  {
    Birthdate : function(lg) {
    
    var Month = {
      en : ["January","February","March","April","May","June","July","August","September","October","November","December"],
      fr : ["janvier","février","mars","avril","mai","juin","juillet","août","septembre","octobre","novembre","décembre"]
    }
    function init()
    {
      this.lg = lg;
      $(".birthdate").each(function(){
        _configureBirthDate($(this));
      });
    }
    
    init();
    
    function _getMonthHtml(month)
    {
      var beginselect =  '<select class="dobfield month">';
      var monthList = Month[this.lg];
      var content = "";
      for(var i = 0; i < (monthList.length-1); i++)
      {
        if(month === i) {
            content += "<option selected=selected value='" + i + "'>" + monthList[i] + "</option>";
        } else {
          content += "<option value='" + i + "'>" + monthList[i] + "</option>";
        }
      }
      var endSelect = '</select>';
      return (beginselect + content + endSelect);
    }
    
    function _getDayHtml(day)
    {
      if(day) {
        if(day < 10)
        {
          day = "0"+day;
        }
        return '<input type="text" class="day dobfield" value="' + day + '"/>';
      } else {
        return '<input type="text" class="day dobfield" placeholder="DD" value=""/>';
      }
    }
    
    function _getYear(year)
    {
      if(year) {
        return '<input type="text" class="yearlong dobfield" value="' + year + '"/>';
      }
      else {
        return '<input type="text" class="yearlong dobfield" placeholder="YYYY" value=""/>';
      }
    }
    
    function _configureBirthDate(el)
    {
      var value, inititalValue, year, month, day, content;
      
      value = el.val();
      inititalValue = Date.parse(value);
      if(inititalValue)
      {
        year = inititalValue.getFullYear();
        month = inititalValue.getMonth();
        day = inititalValue.getDate();
      }
      
      content = _getMonthHtml(month) + _getDayHtml(day) + _getYear(year);

      el.parent().append(content);
      //bind event
      $('.dobfield').change(function () {
        var triggerChange = true;
        var parent = $(this).parent();
        var answer = parent.find('.birthdate');
        var yearval = parent.find('.yearlong').val();
        var dayval = parent.find('.day').val();
        var monthval = parent.find('.month').val();
        //Test Year
        yearInInt = parseInt(yearval);
        if (!isNaN(yearInInt) && Date.validateYear(yearInInt)) {
          if (yearval > Date.today().getFullYear()) {
              $(parent.find('.yearlong')).addClass('error');
              triggerChange = false;
          } else {
              $(parent.find('.yearlong')).removeClass('error');
          }
        }
        else {
          triggerChange = false;
          $(parent.find('.yearlong')).addClass('error');
        }

        //Fix the day when you put a 0 in front of a single number
        if (dayval.length > 0 && dayval.charAt(0) == '0') {
            dayval = dayval.substr(1, dayval.length);
        }
        dayinInt = parseInt(dayval);
        if (!isNaN(dayinInt) && dayinInt <= 31 && dayinInt > 0) {
            try {
                Date.validateDay(dayinInt, yearInInt, (parseInt(monthval) - 1));
                $(parent.find('.day')).removeClass('error');
            }
            catch (err) {
                $(parent.find('.day')).addClass('error');
                triggerChange = false;
            }
        } else {
            $(parent.find('.day')).addClass('error');
        }
        if (triggerChange) {
            var date = Date.today().set({ year: parseInt(yearval), month: parseInt(monthval) - 1, day: parseInt(dayval) });
            answer.val(date.toISOString()).change();
        } else {
            answer.val(date);
        }
      });
    }
  }
});