JavaScriptで文字列と日付を変換する方法

dateToString: function(date){ 
  var year = date.getFullYear(); 
  var month =(date.getMonth() + 1).toString(); 
  var day = (date.getDate()).toString();  
  if (month.length == 1) { 
      month = "0" + month; 
  } 
  if (day.length == 1) { 
      day = "0" + day; 
  }
  var dateTime = year + "-" + month + "-" + day;
  return dateTime; 
},

stringToDate : function(dateStr,separator){
     if(!separator){
            separator="-";
     }
     var dateArr = dateStr.split(separator);
     var year = parseInt(dateArr[0]);
     var month;
     //处理月份为04这样的情况                         
     if(dateArr[1].indexOf("0") == 0){
         month = parseInt(dateArr[1].substring(1));
     }else{
          month = parseInt(dateArr[1]);
     }
     var day = parseInt(dateArr[2]);
     var date = new Date(year,month -1,day);
     return date;
 },