js获取当前日期的前一天、一月、一年的日期

function getYestoday(date){    
	var yesterday_milliseconds=date.getTime()-1000*60*60*24;     
	var yesterday = new Date();     
	    yesterday.setTime(yesterday_milliseconds);     
	  
	var strYear = yesterday.getFullYear();  
	var strDay = yesterday.getDate();  
	var strMonth = yesterday.getMonth()+1;
	if(strMonth<10)  
	{  
		strMonth="0"+strMonth;  
	}  
	datastr = strYear+"-"+strMonth+"-"+strDay;
	return datastr;
  }
  
  //获得上个月在昨天这一天的日期
  function getLastMonthYestdy(date){
     var daysInMonth = new Array([0],[31],[28],[31],[30],[31],[30],[31],[31],[30],[31],[30],[31]);
	 var strYear = date.getFullYear();  
	 var strDay = date.getDate();  
	 var strMonth = date.getMonth()+1;
	 if(strYear%4 == 0 && strYear%100 != 0){
		daysInMonth[2] = 29;
	 }
	 if(strMonth - 1 == 0)
	 {
		strYear -= 1;
		strMonth = 12;
	 }
	 else
	 {
		strMonth -= 1;
	 }
     strDay = daysInMonth[strMonth] >= strDay ? strDay : daysInMonth[strMonth];
	 if(strMonth<10)  
	 {  
		strMonth="0"+strMonth;  
	 }
	 if(strDay<10)  
	 {  
		strDay="0"+strDay;  
	 }
	 datastr = strYear+"-"+strMonth+"-"+strDay;
	 return datastr;
  }
  
  //获得上一年在昨天这一天的日期
  function getLastYearYestdy(date){
	 var strYear = date.getFullYear() - 1;  
	 var strDay = date.getDate();  
	 var strMonth = date.getMonth()+1;
	 if(strMonth<10)  
	 {  
		strMonth="0"+strMonth;  
	 }
	 if(strDay<10)  
	 {  
		strDay="0"+strDay;  
	 }
	 datastr = strYear+"-"+strMonth+"-"+strDay;
	 return datastr;
  }