JS两个字符串日期相减得出天数

// 时间差获取天数
            getDaysByDateString(dateString1,dateString2){
                var  startDate=Date.parse(dateString1.replace('/-/g','/'));  
                var  endDate=Date.parse(dateString2.replace('/-/g','/')); 
                var diffDate=(endDate-startDate)+1*24*60*60*1000;  
                var days=diffDate/(1*24*60*60*1000);  
                return  days;  
            },// 时间差获取天数
            getDaysByDateSt