jQuery+ localStorage 实现一个简易的计时器

Arce

原型

图片发自简书App
需求
1.关闭浏览器时时间继续运行
2.刷新时保持当前状态
3.结束时间保存在客户端

<div class="wrapper">
      <div class="app">
        <div class="container stopwatch">
          
          <div class="clock inactive z-depth-1">
            <span>0:00:00</span>
          <!--  <div class="overlay waves-effect"></div>-->
          </div>
          
          <form>
            <a id="stopwatch-btn-start" class="waves-effect waves-teal btn-flat">开始</a>
        
          </form>
          
        </div>
      </div>
    </div>

<script>
  
  // Stopwatch
var stopwatchInterval = 0;    // The interval for our loop.循环的间隔。 
var stopwatchClock = $(".container.stopwatch").find(".clock"),
  stopwatchDigits = stopwatchClock.find('span');
// 检查前一个会话是否在秒表运行时结束。 
//  如果是的话，按时间重新开始。 
//即 关闭浏览器，点击开始，在后台保持计时的状态
if(Number(localStorage.stopwatchBeginingTimestamp) && Number(localStorage.stopwatchRunningTime)){
  var runningTime = Number(localStorage.stopwatchRunningTime) + new Date().getTime() - Number(localStorage.stopwatchBeginingTimestamp);
  localStorage.stopwatchRunningTime = runningTime;
  startStopwatch();
}

//如果前一个会话有运行时间，就把它写在时钟上。
// 如果没有初始化为0。 
//即结束时不可刷新
if(localStorage.stopwatchRunningTime){
  
  stopwatchDigits.text(returnFormattedToMilliseconds(Number(localStorage.stopwatchRunningTime)));
  
}
else{
  localStorage.stopwatchRunningTime = 0;
}

 /* 实现开始结束 */
    $("#stopwatch-btn-start").toggle(function() {
       $(this).text ('开始').css("background", "#3bb4f2");
        if(stopwatchClock.hasClass('inactive')){
        startStopwatch()
  }
      
    }, function() {
       
        $(this).text ('结束').css("background", "red");
        pauseStopwatch();
    })
    

// Pressing the clock will pause/unpause the stopwatch.
//按下暂停/恢复的时钟秒表
/*stopwatchClock.on('click',function(){
  if(stopwatchClock.hasClass('inactive')){
    startStopwatch()
  }
  else{
    pauseStopwatch();
  }
});*/

/*开始计时*/
function startStopwatch(){
  // 防止多个间隔同时进行。 
  clearInterval(stopwatchInterval);
  var startTimestamp = new Date().getTime(),
    runningTime = 0;
  localStorage.stopwatchBeginingTimestamp = startTimestamp;
  // 应用程序还记得上一次会话运行了多长时间。 
  if(Number(localStorage.stopwatchRunningTime)){
    runningTime = Number(localStorage.stopwatchRunningTime);
  }
  else{
    localStorage.stopwatchRunningTime = 1;
  }
  // 每隔100ms重新计算运行时间，计算公式是 
  //   当你上次启动时钟+上次运行时间 
  stopwatchInterval = setInterval(function () {
    var stopwatchTime = (new Date().getTime() - startTimestamp + runningTime);
    stopwatchDigits.text(returnFormattedToMilliseconds(stopwatchTime));
  }, 100);
  stopwatchClock.removeClass('inactive');
}
/*停止计时*/
function pauseStopwatch(){
  //  停止计时  
  clearInterval(stopwatchInterval);
  if(Number(localStorage.stopwatchBeginingTimestamp)){
    // 计算运行时间。 
    // 新的运行时间=上次运行时间+现在-最后一次启动 
    var runningTime = Number(localStorage.stopwatchRunningTime) + new Date().getTime() - Number(localStorage.stopwatchBeginingTimestamp);
    localStorage.stopwatchBeginingTimestamp = 0;
    localStorage.stopwatchRunningTime = runningTime;
    stopwatchClock.addClass('inactive');
  }
}
// 重置.
/*function resetStopwatch(){
  clearInterval(stopwatchInterval);
  stopwatchDigits.text(returnFormattedToMilliseconds(0));
  localStorage.stopwatchBeginingTimestamp = 0;
  localStorage.stopwatchRunningTime = 0;
  stopwatchClock.addClass('inactive');
}
*/
function returnFormattedToMilliseconds(time){
  var 
    seconds = Math.floor((time/1000) % 60),
    minutes = Math.floor((time/(1000*60)) % 60),
    hours = Math.floor((time/(1000*60*60)) % 24);
  seconds = seconds < 10 ? '0' + seconds : seconds;
  minutes = minutes < 10 ? '0' + minutes : minutes;
   return hours + ":" + minutes + ":" + seconds;
}
</script>

完整的demo下载链接：https://pan.baidu.com/s/1kVOmt4V 密码：rfqq
原文作者：祈澈姑娘
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