js获取指定日期的前一天

function getYesterday(date) {
     var date = date.split('-'),
     today = new Date().setFullYear(+date[0], +date[1]-1, +date[2]), 
     yesterday = new Date(today - 24 * 60 * 60 * 1000);
     var y = yesterday.getFullYear();
     var m = yesterday.getMonth() + 1;
     var d = yesterday.getDate();
     if(m<10){
       m = '0'+m;   
     }
     if(d<10){
          d = '0'+d; 
     }
  
    return y+''+m+''+d;  
 }
 getYesterday("20140421");