js 设置日期函数

前三十天: 

var now = new Date();
var prev = now.setDate( now.getDate() - 30 )
vm.sDate = comm.getFormatDate( new Date(prev) , '-', '00:00' );

getFormatDate: function (date, format, hm){
         var  res = '',
              y, m , d, hours, minute;
       
        function toDoubleTime(time){
            var s, arr = [], ele, i, len, res = [];

            // 0 也不能忽略
            if( typeof time == "undefined" ){
                s = '';
            }else{
                s = time;
            }
            
            arr = (s+'').split(':');
            
            if( arr.length > 1 ){      
                for(i=0, len=arr.length; i<len; i++ ){
                    ele = arr[i];
                    ele = ele.trim();
                    
                    ele.length < 2 ? (ele = '0' + ele) : ele;
                    
                    res.push(ele);
                }
                
                return res.join(' : ');
            }else{
                ele = s + '';
                ele.length < 2 ? (ele = '0' + ele) : ele;
                return ele;
            }
        }
             
        y = date.getFullYear();
        m = date.getMonth() + 1;
        d = date.getDate();
                
        hours = date.getHours();
        minute = date.getMinutes();   
        
        if( hm ){
            hours = hm.split(':')[0] || '';
            minute = hm.split(':')[1] || '';
        }     
    
        switch (format){
            case '-':
                res = y + '-' + toDoubleTime(m) + '-' + toDoubleTime(d) + ' ' + toDoubleTime(hours) + ':' + toDoubleTime(minute);
                break;
            case '/':
                res = y + '/' + m + '/' + d + ' ' + hours + ':' + minute;
                break;    
            case 'zh':
                res = y + '年' + m + '月' + d + '日  ' + hours + ':' + minute;
                break;    
        }
            
        return res;
    }