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

<script> 
 // Stopwatch
var stopwatchInterval = 0; // The interval for our loop.循環的間隔。 
var stopwatchClock = $(".container.stopwatch").find(".clock"),
 stopwatchDigits = stopwatchClock.find('span');
// 檢查前一個會話是否在秒表運行時結束。 
// 如果是的話，按時間重新開始。 
//即 關閉瀏覽器，點擊開始，在后臺保持計時的狀態
if(Number(localStorage.stopwatchBeginingTimestamp) && Number(localStorage.stopwatchRunningTime)){
 var runningTime = Number(localStorage.stopwatchRunningTime) + new Date().getTime() - Number(localStorage.stopwatchBeginingTimestamp);
 localStorage.stopwatchRunningTime = runningTime;
 startStopwatch();
}
//如果前一個會話有運行時間，就把它寫在時鐘上。
// 如果沒有初始化為0。 
//即結束時不可刷新
if(localStorage.stopwatchRunningTime){
 stopwatchDigits.text(returnFormattedToMilliseconds(Number(localStorage.stopwatchRunningTime)));
}
else{
 localStorage.stopwatchRunningTime = 0;
}
 /* 實現開始結束 */
 $("#stopwatch-btn-start").toggle(function() {
 $(this).text ('開始').css("background", "#3bb4f2");
 if(stopwatchClock.hasClass('inactive')){
 startStopwatch()
 } 
 }, function() { 
 $(this).text ('結束').css("background", "red");
 pauseStopwatch();
 }) 
// Pressing the clock will pause/unpause the stopwatch.
//按下暫停/恢復的時鐘秒表
/*stopwatchClock.on('click',function(){
 if(stopwatchClock.hasClass('inactive')){
 startStopwatch()
 }
 else{
 pauseStopwatch();
 }
});*/
/*開始計時*/
function startStopwatch(){
 // 防止多個間隔同時進行。 
 clearInterval(stopwatchInterval);
 var startTimestamp = new Date().getTime(),
 runningTime = 0;
 localStorage.stopwatchBeginingTimestamp = startTimestamp;
 // 應用程序還記得上一次會話運行了多長時間。 
 if(Number(localStorage.stopwatchRunningTime)){
 runningTime = Number(localStorage.stopwatchRunningTime);
 }
 else{
 localStorage.stopwatchRunningTime = 1;
 }
 // 每隔100ms重新計算運行時間，計算公式是 
 // 當你上次啟動時鐘+上次運行時間 
 stopwatchInterval = setInterval(function () {
 var stopwatchTime = (new Date().getTime() - startTimestamp + runningTime);
 stopwatchDigits.text(returnFormattedToMilliseconds(stopwatchTime));
 }, 100);
 stopwatchClock.removeClass('inactive');
}
/*停止計時*/
function pauseStopwatch(){
 // 停止計時 
 clearInterval(stopwatchInterval);
 if(Number(localStorage.stopwatchBeginingTimestamp)){
 // 計算運行時間。 
 // 新的運行時間=上次運行時間+現在-最后一次啟動 
 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>