mounted () {
  // 页面加载完后显示当前时间
  this.realTime = this.dealWithTime(new Date())
  // 定时刷新时间
  let _this = this
  // 定时器
  this.timer = setInterval(function () {
    _this.realTime = _this.dealWithTime(new Date()) // 修改数据date
  }, 1000)
},
methods: {
  dealWithTime (data) {
      let formatDateTime
      let Y = data.getFullYear()
      let M = data.getMonth() + 1
      let D = data.getDate()
      let H = data.getHours()
      let Min = data.getMinutes()
      let S = data.getSeconds()
      let W = data.getDay()
      H = H < 10 ? ('0' + H) : H
      Min = Min < 10 ? ('0' + Min) : Min
      S = S < 10 ? ('0' + S) : S
      switch (W) {
        case 0:
          W = '天'
          break
        case 1:
          W = '一'
          break
        case 2:
          W = '二'
          break
        case 3:
          W = '三'
          break
        case 4:
          W = '四'
          break
        case 5:
          W = '五'
          break
        case 6:
          W = '六'
          break
        default:
          break
      }
      formatDateTime = Y + '年' + M + '月' + D + '日 ' + H + ':' + Min + ':' + S + ' 星期' + W
      return formatDateTime
  }
},
// 注意在vue实例销毁前，清除我们的定时器。
destroyed () {
  if (this.timer) { 
    clearInterval(this.timer)
  }
}

this.realTime 即为处理后的当前时间。