小程序倒计时，刷新页面不重置

onShow:function(){
  console.log(this.data.countDown)
var djsendtime = wx.getStorageSync('djsendtime');
console.log(djsendtime)
if (djsendtime != undefined && !isNaN(djsendtime) && djsendtime !='') {
	var now = new Date().getTime();  //当前时间戳
  var locksecends = parseInt((djsendtime - now) / 1000);
  
	if (locksecends <= 0) {
		wx.removeStorageSync("djsendtime");
	} else {
		this.LockButton(locksecends);
	}
}else{
  this.LockButton(this.data.countDown);
}
},

这里的countDown是默认时间

LockButton:function(locksecends){
  console.log(locksecends)
  var that=this
  //console.log(locksecends)
	var djsendtime = wx.getStorageSync('djsendtime')
	if (djsendtime == null || djsendtime == undefined || djsendtime == 'undefined' || djsendtime == 'null' || djsendtime=='') {
		var now = new Date().getTime();  //当前时间戳
		var endtime = locksecends * 1000 + now;  //结束时间戳
		wx.setStorageSync('djsendtime', endtime); //将结束时间保存到cookie
	}
	that.setData({
    countDown:locksecends
  })
	var timer = setInterval(function () {
    locksecends--;
    console.log(locksecends)
     that.setData({
       countDown:locksecends
     })
		if (locksecends <= 0) {
			//倒计时结束清除 localStorage值
			wx.removeStorageSync("djsendtime");
			clearInterval(timer); 
		}
	}, 1000);
}

 <view style="position:fixed;top:0;left:200rpx;" class="flex_l_r_c" >
    <view>剩余：{{countDown}}秒</view>
  </view>