jQuery+ localStorage 实现一个简易的计时器

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
原文链接：https://www.jianshu.com/u/05f416aefbe1
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