JS常用的时间处理函数

1.求距离某个日期n天后的日期

function a1(dayStr,nums) {
    
    
    let t1 = new Date(dayStr);
    console.log(t1);
    let t2 = new Date((t1/1000 + 86400*nums)*1000);
    console.log(t2);
    var t3 = t2.getFullYear() + '-' + (t2.getMonth() + 1) + '-' + t2.getDate();
    console.log(t3);


}
a1('2020-01-03',2);  //2020-1-5
a1('2020/01/03',28);  //2020-1-31

2.求两个日期的差值

function a2(day1,day2) {
    
    
    let t1 = Date.parse(day1);
    let t2 = Date.parse(day2);
    console.log(t1,t2);
    let t3 = t1 > t2?t1-t2:t2-t1;
    console.log(t3);
    let t4 = t3/(1*24*60*60*1000);
    console.log(t4);

}
a2('2020-01-03','2020-01-05');   //2
a2('2020/01/03','2019/12/23');   //11