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In-depth JavaScript timer

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Mar 13, 2018 pm 01:26 PM

javascriptjstimer

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!

Recommended reading:

In-depth basic application of JavaScript

##8 basic knowledge that must be paid attention to in JS

The above is the detailed content of In-depth JavaScript timer. For more information, please follow other related articles on the PHP Chinese website!

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