多年积累的js日期代码倾情奉献,该如何处理

<script language=Javascript>String.prototype.Left = function(len){        if(isNaN(len)||len==null){                len = 0;        } else {         if(parseInt(len)<0||parseInt(len)>this.length) {                        len = 0;                }        }        return this.substr(0,this.length-len)+'**';}//日期自动补零程序function appendZero(n){        return(("00"+ n).substr(("00"+ n).length-2));}//获得当年当月最大天数function GetMonthMaxDay(theYear,theMonth){    var theDays = new Array(31,28,31,30,31,30,31,31,30,31,30,31);  var theMonthDay = 0, tmpYear = this.formatYear(theYear);  theMonthDay = theDays[theMonth];  if (theMonth == 1){ //theMonth is February          if (((tmpYear % 4 == 0) && (tmpYear % 100 != 0)) || (tmpYear % 400 == 0)){                  theMonthDay++;          }  }  return(theMonthDay);}//把年份格式化成4位function formatYear(theYear){    var tmpYear = parseInt(theYear,10);  if (tmpYear < 100){  tmpYear += 1900;  if (tmpYear < 1940){  tmpYear += 100;  }  }  if (tmpYear < this.MinYear){  tmpYear = this.MinYear;  }  if (tmpYear > this.MaxYear){  tmpYear = this.MaxYear;  }  return(tmpYear);}