JS获取前一天时间

 	     var today=new Date();
          var yesterday_milliseconds=today.getTime()+(1*(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;   
          }   
          var strYesterday=strYear+"-"+strMonth+"-"+strDay; var today=new Date();
          var yest