BOM系列第三篇之定时器应用(时钟、倒计时、秒表和闹钟)

2019-11-20 09:13:27

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时钟

　　最简单的时钟制作办法是通过正则表达式的exec()方法，将时间对象的字符串中的时间部分截取出来，使用定时器刷新即可

<div id="myDiv"></div><script>myDiv.innerHTML = //d/d:/d/d:/d/d/.exec(new Date().toString())[0];setInterval(function(){myDiv.innerHTML = //d/d:/d/d:/d/d/.exec(new Date().toString())[0]; },500);</script>

倒计时

【1】简易倒计时

　　简易倒计时就是每1s通过setInterval将设置的时间减去1来达到要求

<div id="myDiv"><label for="set"><input type="number" id="set" step="1" value="0">秒</label><button id="btn">确定</button><button id="reset">重置</button> </div><script>var timer;reset.onclick = function(){history.go();}btn.onclick = function(){if(timer) return;set.setAttribute('disabled','disabled');timer = setInterval(function(){if(Number(set.value) === 0){clearInterval(timer);timer = 0;set.removeAttribute('disabled');return;}set.value = Number(set.value) - 1;},1000);} </script>

【2】精确倒计时

　　由定时器的运行机制，我们知道每间隔1000ms去改变时间的作法并不可靠。更精确地做法，应该是与系统的运行时间作为参照，倒计时的时间变化与系统的时间变化同步，达到精确倒计时的效果　

　　[注意]此部分中，需要通过取模运算和除法运算进行时、分、秒的计算，详细情况移步至此

<div id="myDiv"><label for="hour"><input type="number" id="hour" min="0" max="23" step="1" value="0" />时</label><label for="minute"><input type="number" id="minute" min="0" max="59" step="1" value="0" />分</label><label for="second"><input type="number" id="second" min="0" max="23" step="1" value="0" />秒</label><button id="btn">确定</button><button id="reset">重置</button></div><script>var timer;//输入限制hour.onchange = function(){if(Number(this.value) !== Number(this.value)) this.value = 0;if(this.value > 23) this.value = 23;if(this.value < 0) this.value = 0;}second.onchange = minute.onchange = function(){if(Number(this.value) !== Number(this.value)) this.value = 0;if(this.value > 59) this.value = 59;if(this.value < 0) this.value = 0;}reset.onclick = function(){history.go();}btn.onclick = function(){if(timer) return;for(var i = 0; i < 3; i++){myDiv.getElementsByTagName('input')[i].setAttribute('disabled','disabled');}//原始储存值var setOri = hour.value*3600 + minute.value*60 + second.value*1;//原始系统时间值var timeOri = (new Date()).getTime();//现在所剩时间值var setNow;cancelAnimationFrame(timer);timer = requestAnimationFrame(function fn(){//当前系统时间值var timeNow = (new Date()).getTime();//使系统时间的差值与设置时间的差值相等，来获得正常的时间变化setNow = setOri - Math.floor((timeNow - timeOri)/1000);hour.value = Math.floor((setNow%86400)/3600);minute.value = Math.floor((setNow%3600)/60);second.value = Math.floor(setNow%60);timer = requestAnimationFrame(fn);if(setNow==0){cancelAnimationFrame(timer);timer = 0;btn.innerHTML = '计时结束';for(var i = 0; i < 3; i++){myDiv.getElementsByTagName('input')[i].removeAttribute('disabled');}setTimeout(function(){btn.innerHTML = '确定';},1000) }})}</script>

秒表

【1】简易秒表

　　秒表与倒计时的思路相同，相比而言，更加简单。每间隔100ms增加100ms即可

<div id="myDiv"><label for="set"><input id="set" value="0"></label><button id="btn">开始</button><button id="reset">重置</button> </div><script>var timer;var con = 'off';var num = 0;reset.onclick = function(){history.go();}btn.onclick = function(){if(con === 'off'){set.setAttribute('disabled','disabled');con = 'on';btn.innerHTML = '暂停';timer = setInterval(function(){num+= 100;var minute = Math.floor(num/1000/60);var second = Math.floor(num/1000);var ms = Math.floor(num%1000)/100;set.value = minute + ' : ' + second + ' . ' + ms; },100);}else{clearInterval(timer);con = 'off';btn.innerHTML = '开始'; }} </script>

【2】精确秒表

　　与倒计时类似，使用计时器的时间间隔作为时间变化的参照是不准确的。更精确的做法，应该是使用系统的时间变化作为秒表的变化的参照

<div id="myDiv"><label for="set"><input id="set" value="0"></label><button id="btn">开始</button><button id="reset">重置</button> </div><script>var timer;var con = 'off';//ori表示初始的系统时间var ori;//dis表示当前运行时的秒数(动态)var dis = 0;//last储存暂停时的秒数(静态)var last = 0;reset.onclick = function(){history.go();}btn.onclick = function(){if(con === 'off'){set.setAttribute('disabled','disabled');con = 'on';btn.innerHTML = '暂停';//保留已经走过的秒数的系统时间ori = (new Date()).getTime() - last; timer = requestAnimationFrame(function fn(){dis = (new Date()).getTime() - ori;cancelAnimationFrame(timer);timer = requestAnimationFrame(fn);var minute = Math.floor(dis/1000/60);var second = Math.floor(dis/1000);var ms = Math.floor(dis%1000);set.value = minute + ' : ' + second + ' . ' + ms; });}else{cancelAnimationFrame(timer);btn.innerHTML = '开始'; con = 'off';last = dis;}} </script>

闹钟

　　闹钟其实就是在时钟的基础上增加一个预定时间设置，闹钟设置需要将设置时间转换成距离1970年1月1日的毫秒数，然后再算出与当前时间的差值。随着当前时间的不断增加，当差值为0时，闹钟响起

<div id="myDiv"></div><div id="con"><label for="hour"><input type="number" id="hour" min="0" max="23" step="1" value="0" />时</label><label for="minute"><input type="number" id="minute" min="0" max="59" step="1" value="0" />分</label><label for="second"><input type="number" id="second" min="0" max="23" step="1" value="0" />秒</label><button id="btn">确定</button><button id="reset">重置</button></div><div id="show"></div><script>var timer;//所剩时间var dis;myDiv.innerHTML = //d/d:/d/d:/d/d/.exec(new Date().toString())[0];setInterval(function(){myDiv.innerHTML = //d/d:/d/d:/d/d/.exec(new Date().toString())[0]; },100);reset.onclick = function(){history.go();}btn.onclick = function(){//原始储存值var setOri = hour.value*3600 + minute.value*60 + second.value*1;//原始值转换为1970年的毫秒数var setMs = +new Date(new Date().toDateString()) + setOri*1000;//如果设置的时间早于当前时间，则设置无效if(setMs < +new Date()){return;}for(var i = 0; i < 3; i++){con.getElementsByTagName('input')[i].setAttribute('disabled','disabled');}cancelAnimationFrame(timer);timer = requestAnimationFrame(function fn(){//算出设置时间与当前时间的差值dis = Math.ceil((setMs - (new Date()).getTime())/1000);var showHour = Math.floor((dis%86400)/3600);var showMinute = Math.floor((dis%3600)/60);var showSecond = Math.floor(dis%60);timer = requestAnimationFrame(fn);show.innerHTML = '距离预定时间还有 ' + showHour + '小时 ' + showMinute + '分 ' + showSecond + '秒';//当差值为0时，时间到if(dis==0){cancelAnimationFrame(timer);btn.innerHTML = '时间到了';for(var i = 0; i < 3; i++){con.getElementsByTagName('input')[i].removeAttribute('disabled');}timer = setTimeout(function(){btn.innerHTML = '确定';},1000) }});}</script>