java脚本倒计时计时器在页面刷新时重置

var timer;
var compareDate = new Date();
compareDate.setDate(compareDate.getDate() + 16); //incresed by to date + (16 days)

timer = setInterval(function() {
  timeBetweenDates(compareDate);
}, 1000);

function timeBetweenDates(toDate) {
  var dateEntered = toDate;
  var now = new Date();
  var difference = dateEntered.getTime() - now.getTime();

  if (difference <= 0) {

    // Timer done
    clearInterval(timer);

  } else {

    var seconds = Math.floor(difference / 1000);
    var minutes = Math.floor(seconds / 60);
    var hours = Math.floor(minutes / 60);
    var days = Math.floor(hours / 24);

    hours %= 24;
    minutes %= 60;
    seconds %= 60;

    $("#days").text(days);
    $("#hours").text(hours);
    $("#minutes").text(minutes);
    $("#seconds").text(seconds);
  }
}

body {
  background: #f5f5f5;
}
#timer {
  font-family: Arial, sans-serif;
  font-size: 20px;
  color: #999;
  letter-spacing: -1px;
}
#timer span {
  font-size: 60px;
  color: #333;
  margin: 0 3px 0 15px;
}
#timer span:first-child {
  margin-left: 0;
}
  

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>


<div id="timer">
  <span id="days"></span>days
  <span id="hours"></span>hours
  <span id="minutes"></span>minutes
  <span id="seconds"></span>seconds
</div>