12行计算两个时间差，返回00:00:00格式

12行计算两个时间差，返回00:00:00格式
直播时间用

    let a = 'Thu Aug 20 2020 24:00:00 GMT+0800 (中国标准时间)'
    let b = 'Thu Aug 22 2020 01:30:10 GMT+0800 (中国标准时间)'
    function getHis(a, b) {
      let an = new Date(a).getTime()
      let bn = new Date(b).getTime()
      let diff = bn - an
      let max = 24 * 60 * 60 * 1000
      // 处理大于24小时的情况
      if(diff > max) diff = diff % max
      // 取余取整
      let h = ~~(diff/1000 % 24)
      let i = ~~(diff/1000/24 % 60)
      let s = ~~(diff/1000/24/60 % 60)
      // 补零
      if(h < 10 ) h = h + '0'
      if(i < 10 ) i = i + '0'
      if(s < 10 ) s = s + '0'
      return `${h}:${i}:${s}`
    }
    let c = getHis(a,b)
    console.log(c)