运动-无缝滚动

一、布局

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
    *{
        list-style: none;
        margin: 0;
        padding: 0;
    }

    #box{
        840px;
        position: relative;
        height: 210px;
        overflow: hidden; 
    }

    #box ul{
        height: 210px;
        position: absolute;
    }

    #box ul li{
        200px;
        height: 200px;
        float: left;
        padding: 5px;
    }

    #box ul li img{
        200px;
        height: 200px;

    }

    #bigbox{
        position: relative;
        840px;
        border: 1px solid #000;
        margin: 100px auto;
    }

    #bigbox a{
        position: absolute;    
        top:50%;
        margin-top:-30px;            
    }

    #bigbox a.left {
        left: -60px;
    }

    #bigbox a.right {
        right: -60px;        
    }    

    </style>
</head>
<body>
<div id="bigbox">
    <a href="javascript:;" class='left'><img src="../img/left.png" alt=""></a>
    <a href="javascript:;" class="right"><img src="../img/right.png" alt=""></a>
    <div id="box">
        <ul>
            <li><img src="../img/cat/1.jpg" alt=""></li>
            <li><img src="../img/cat/2.jpg" alt=""></li>
            <li><img src="../img/cat/3.jpg" alt=""></li>
            <li><img src="../img/cat/4.jpg" alt=""></li>
        </ul>

    </div>        
</div>
</body>
</html>

二、获取需要操作的元素

var oBox=document.getElementById('box');
var oBigBox=document.getElementById('bigbox');
var oUl=oBox.getElementsByTagName('ul')[0];
var aLi=oUl.children;
var leftBtn=oBigBox.children[0];
var rightBtn=oBigBox.children[1];

三、做无缝滚动，需要将ul的内容复制一份，并让ul的内容在一行显示，所以我们执行以下操作：

oUl.innerHTML+=oUl.innerHTML; //将ul的内容复制一份
oUl.style.width=aLi[0].offsetWidth*aLi.length+'px';  //重新计算ul的宽度

四、首先我们分析向左运动的情况：

五、分析向右运动的情况：

完整代码：

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
    *{
        list-style: none;
        margin: 0;
        padding: 0;
    }

    #box{
        840px;
        position: relative;
        height: 210px;
        overflow: hidden; 
    }

    #box ul{
        height: 210px;
        position: absolute;
    }

    #box ul li{
        200px;
        height: 200px;
        float: left;
        padding: 5px;
    }

    #box ul li img{
        200px;
        height: 200px;

    }

    #bigbox{
        position: relative;
        840px;
        border: 1px solid #000;
        margin: 100px auto;
    }

    #bigbox a{
        position: absolute;    
        top:50%;
        margin-top:-30px;            
    }

    #bigbox a.left {
        left: -60px;
    }

    #bigbox a.right {
        right: -60px;        
    }    

    </style>
    <script>
    window.onload=function(){
        var oBox=document.getElementById('box');
        var oBigBox=document.getElementById('bigbox');
        var oUl=oBox.getElementsByTagName('ul')[0];
        var aLi=oUl.children;
        var leftBtn=oBigBox.children[0];
        var rightBtn=oBigBox.children[1];
        var timer=null;


        
        oUl.innerHTML+=oUl.innerHTML;
        oUl.style.width=aLi[0].offsetWidth*aLi.length+'px';
        
        var left=0;
        var W = oUl.offsetWidth/2;
        var bsin = true;


        function run(num){
            clearInterval(timer);
            timer=setInterval(function(){
                if(bsin){
                    left+=num;
                    if(left<0){
                        oUl.style.left=left%W+'px';
                    }else{
                        oUl.style.left=-(W-left%W)+'px';
                    }                    
                }

                
            },30);                

        };

        run(-10);

    

        leftBtn.onclick=function(){
            run(-10); //你好
        }

        rightBtn.onclick=function(){
            run(10);
        }

        oBox.onmouseover=function(){
            bsin=false;
        }

        oBox.onmouseout=function(){
            bsin=true;
        }
    }
    </script>
</head>
<body>
<div id="bigbox">
    <a href="javascript:;" class='left'><img src="../img/left.png" alt=""></a>
    <a href="javascript:;" class="right"><img src="../img/right.png" alt=""></a>
    <div id="box">
        <ul>
            <li><img src="../img/cat/1.jpg" alt=""></li>
            <li><img src="../img/cat/2.jpg" alt=""></li>
            <li><img src="../img/cat/3.jpg" alt=""></li>
            <li><img src="../img/cat/4.jpg" alt=""></li>
        </ul>

    </div>        
</div>
</body>
</html>

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原文地址：https://www.cnblogs.com/xuxiaozhi/p/10209076.html