计算两个日期之间所隔天数

var date1 = new Date("06/30/2019"); 
var date2 = new Date("07/30/2019"); 
var Difference_In_Time = date2.getTime() - date1.getTime(); 
var Difference_In_Days = Difference_In_Time / (1000 * 3600 * 24);