Home >Web Front-end >JS Tutorial >In-depth JavaScript timer

In-depth JavaScript timer

php中世界最好的语言Original: 2018-03-13 13:26:381487browse

This time I will bring you an in-depth introduction to JavaScript timers. What are the precautions for using JavaScript timers? The following is a practical case, let’s take a look.

Get the year, month, day, week, hour, minute and second

<script>
    var date = new Date()
    date.getFullYear(); //2017 年
    date.getMonth(); // 5 注意:月份是个诡异的东西,他是从0开始计算的,故+1才等于正常的月份
    date.getDate(); //11 日
    date.getDay(); //星期 美国的星期是从星期日开始的,故0为星期日,1为星期一,...6为星期六
    date.getHours(); //时
    date.getMinutes(); //分
    date.getSeconds(); //秒
</script>

2. Timer

setInterval Interval type: How many milliseconds should be executed every time

setTimeout Delay type: How much delay ms execution

The difference between the two timers:

setInterval interval type, can be executed multiple times

setTimeout delay type, only executed once

<script>
        function show() {
            alert(&#39;定时器&#39;);
        }//        setInterval(show,1000); // 一秒执行一次
        setTimeout(show,1000);  //延时一秒执行
</script>

Start the timer setInterval()

var btn1 = document.getElementById(&#39;btn1&#39;);var btn2 = document.getElementById(&#39;btn2&#39;);var i = 0;var timer = null;
btn1.onclick = function () {       //开启定时器
       timer = setInterval(function () {
           i++;
           alert(i);
      },1000);
}

Close the timer clearInterval(timer);

btn2.onclick = function () {
       i = 0;
       clearInterval(timer);
}

3. Intercept string

str[0];不兼容低版本浏览器,如IE7等;
var a = &#39;abcdef&#39;;alert(a[0]);
str.charAt(0); 兼容各种浏览器
var a = &#39;abcdef&#39;;a.charAt(0); //兼容各种浏览器

4. Digital clock exercise

<html lang="en"><head>
    <meta charset="UTF-8">
    <title>数字时钟</title>
    <style>
        body{            background-color: black;            font-size: 50px;            color: white;
        }    </style>
    <script>
        window.onload = function () {            var aImg = document.getElementsByTagName(&#39;img&#39;);            function tick() {                var date = new Date();                //把时间拼接成一个字符串,如:212835;
                //toDouble()这个函数,是为了把单数转换成双位数,如,9转换成09
                var sTime = toDouble(date.getHours()) + toDouble(date.getMinutes()) + toDouble(date.getSeconds());                for (var i=0;i<aImg.length;i++){
                    aImg[i].src = &#39;image/&#39;+sTime.charAt(i)+&#39;.png&#39;;
                }
            }
            setInterval(tick,1000);
            tick(); //由于setInterval会延时1000ms执行,所以为了防止每次刷新页面时,页面上显示00:00:00的情况,调用下此函数
        }        //把获取的时/分/秒 转换成双位数
        function toDouble(n) {            if (n<10){                return &#39;0&#39; + n;
            }else {                return &#39;&#39; +n;//前面的&#39;&#39;,是为了把数字转换成字符串
            }
        }    </script></head><body>![](image/0.png)
![](image/0.png)
:
![](image/0.png)
![](image/0.png)
:
![](image/0.png)
![](image/0.png)</body></html>

In-depth JavaScript timer

Delay prompt box

<html lang="en"> <head>     <meta charset="UTF-8">     <title>07-延时提示框</title>     <style>         div{float: left;margin-left: 20px;}         #div1{width: 50px;height: 50px;background-color: red;}         #div2{ width: 200px;height: 200px;background-color: #ccc;display: none;}     </style>     <script>         window.onload = function () {             var oDiv1 = document.getElementById(&#39;div1&#39;);             var oDiv2 = document.getElementById(&#39;div2&#39;);             var timer = null;             oDiv1.onmouseover = function () {                 oDiv2.style.display = &#39;block&#39;;                 clearTimeout(timer); //清除延时器             }             oDiv1.onmouseout = function () {                 timer = setTimeout(function () {                     oDiv2.style.display = &#39;none&#39;;                 },500);             }             oDiv2.onmouseover = function () {                 clearTimeout(timer);             }             oDiv2.onmouseout = function () {                 timer = setTimeout(function () {                     oDiv2.style.display = &#39;none&#39;;                 },500);             }         }     </script> </head> <body> <div id="div1"></div> <div id="div2"></div> </body> </html>

Simplified code: merge two identical mouseover and mouseout

<html lang="en"> <head>     <meta charset="UTF-8">     <title>07-延时提示框</title>     <style>         div{float: left;margin-left: 20px;}         #div1{width: 50px;height: 50px;background-color: red;}         #div2{ width: 200px;height: 200px;background-color: #ccc;display: none;}     </style>     <script>         window.onload = function () {             var oDiv1 = document.getElementById(&#39;div1&#39;);             var oDiv2 = document.getElementById(&#39;div2&#39;);             var timer = null;             //简化代码,合并两个相同的mouseover             oDiv2.onmouseover = oDiv1.onmouseover = function () {                 oDiv2.style.display = &#39;block&#39;;                 clearTimeout(timer);             }             //简化代码,合并两个相同的mouseout             oDiv2.onmouseout = oDiv1.onmouseout = function () {                 timer = setTimeout(function () {                     oDiv2.style.display = &#39;none&#39;;                 },500);             }         }     </script> </head> <body> <div id="div1"></div> <div id="div2"></div> </body> </html>

6. Seamless scrolling

<html><head><meta charset="utf-8"><title>无缝滚动</title><style>* {margin:0; padding:0;}#div1 {width:712px; height:108px; margin:100px auto; position:relative; background:red; overflow:hidden;}#div1 ul {position:absolute; left:0; top:0;}#div1 ul li {float:left; width:178px; height:108px; list-style:none;}</style><script>window.onload=function (){    var oDiv=document.getElementById(&#39;div1&#39;);    var oUl=oDiv.getElementsByTagName(&#39;ul&#39;)[0];    var aLi=oUl.getElementsByTagName(&#39;li&#39;);    
    var speed=-2;    
    //oUl.innerHTML=oUl.innerHTML+oUl.innerHTML;
    oUl.innerHTML+=oUl.innerHTML;
    oUl.style.width=aLi[0].offsetWidth*aLi.length+&#39;px&#39;;    //offsetWidth :(width+padding+border) 当前对象的宽度。
    //offsetLeft 当前对象到其上级层左边的距离。
    function move(){        //往左滚动
        if(oUl.offsetLeft<-oUl.offsetWidth/2)
        {
            oUl.style.left=&#39;0&#39;;
        }        //往右滚动
        if(oUl.offsetLeft>0)
        {
            oUl.style.left=-oUl.offsetWidth/2+&#39;px&#39;;
        }        //offsetLeft 距离父元素左侧距离
        oUl.style.left=oUl.offsetLeft+speed+&#39;px&#39;;
    }    //定时器
    var timer=setInterval(move, 30);
    
    oDiv.onmouseover=function ()    {
        clearInterval(timer);
    };
    
    oDiv.onmouseout=function ()    {
        timer=setInterval(move, 30);
    };    //往左滚动
    document.getElementsByTagName(&#39;a&#39;)[0].onclick=function ()    {
        speed=-2;
    };    //往右滚动
    document.getElementsByTagName(&#39;a&#39;)[1].onclick=function ()    {
        speed=2;
    };
};</script></head><body><a href="javascript:;">向左走</a><a href="javascript:;">向右走</a><div id="div1">
    <ul>
        <li>![](img2/1.jpg)</li>
        <li>![](img2/2.jpg)</li>
        <li>![](img2/3.jpg)</li>
        <li>![](img2/4.jpg)</li>
    </ul></div></body></html>

Believe After reading the case in this article, you have mastered the method. For more exciting information, please pay attention to other related articles on the PHP Chinese website!

In-depth JavaScript timer

Related articles