javascript根据当前日期获取上个月日期

1 function lastMonthDate(){ 2     var Nowdate = new Date(); 3     var vYear = Nowdate.getFullYear(); 4     var vMon = Nowdate.getMonth() + 1; 5     var vDay = Nowdate.getDate(); 6 　　//每个月的最后一天日期（为了使用月份便于查找，数组第一位设为0） 7     var daysInMonth = new Array(0,31,28,31,30,31,30,31,31,30,31,30,31); 8     if(vMon==1){ 9         vYear = Nowdate.getFullYear()-1;10         vMon = 12;11     }else{12         vMon = vMon -1;13     }14 　　//若是闰年，二月最后一天是29号15     if(vYear%4 == 0 && vYear%100 != 0  || vYear%400 = 0 ){16         daysInMonth[2]= 29;17     }18     if(daysInMonth[vMon] < vDay){19         vDay = daysInMonth[vMon];20     }21     if(vDay<10){22         vDay="0"+vDay;23     }24     if(vMon<10){25         vMon="0"+vMon;26     }27     var date =vYear+"-"+ vMon +"-"+vDay;28     console.log(date)29     return date;30 }