时间-判断两个时间相差多少天

（一）判断两个时间相差多少天

let oldDay = new Date("2020-12-04 15:34:54").getTime()
let newDay = new Date("2020-12-24 21:15:54").getTime()
let cha = parseInt((newDay - oldDay) / (1000 * 60 * 60 * 24))
console.log(cha) // 20

（二）判断与今天相差多少天

let oldDay = new Date("2020-12-04 15:34:54").getTime()
let now = new Date().getTime()
let cha = parseInt((now - oldDay) / (1000 * 60 * 60 * 24))
console.log(cha)