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js实现首页轮播图效果

1、相关技术

获取元素 document.getElementById(“id 名称”)
事件(onload) 只能写一次并且放到body标签中
定时操作:setInterval(“changeImg()”,3000);

2、步骤分析(此案例轮播图效果是基于HTML&CSS——使用DIV和CSS完成网站首页重构实现的)

事先准备三张一样大小的图片(img1、img2、img3)放在文件夹Img下。

第一步:确定事件(onload)并为其绑定一个函数

第二步:书写绑定的这个函数

第三步:书写定时任务(setInterval)

第四步:书写定时任务里面的函数

第五步:通过变量的方式,进行循环(获取轮播图的位置,并设置 src 属性,在循环的时候需要注意到了最后一 张图片的时候要重置)。

<script>
            function init(){
                //书写轮播图显示的定时操作
                setInterval("changImg()",3000);
            }
            
            //书写函数
            var i=1;
            function changImg(){
                i++;
                
                //获取图片位置并设置src属性值
                document.getElementById("img_1").src="../img/"+i+".jpg";
                if(i==3){
                    i=0;
                }
            }
</script>

Html:

<body onload="init()">

在指定位置定义 id。

最终实现的代码如下:

<!DOCTYPE html>
<html>
    <head>
        <meta charset="UTF-8">
        <title>首页</title>
        <style>
            #father{
                border: 0px solid black;
                width: 1300px;
                height: 1600px;
                margin: auto;
            }
            #logo{
                border: 0px solid black;
                width: 1300px;
                height: 50px;
            }
            .top{
                border: 0px solid blue;
                width: 431px;
                height: 50px;
                float: left;
            }
            #top{
                padding-top: 12px;
                height: 38px;
            }
            
            #menu{
                border: 0px solid red;
                width:1300px;
                height: 50px;
                background: black;
                margin-bottom: 10px;
            }
            ul li{
                display: inline;
                color: white;
            }
            #product{
                border: 0px solid goldenrod;
                width: 1300px;
                height: 550px;
            }
            #product_top{
                border: 0px solid blue;
                width: 100%;
                height: 43px;
                padding-top: 5px;
            }
            #product_bottom{
                border: 0px solid green;
                width: 100%;
                height: 498px;
            }
            
            #product_bottom_left{
                border: 0px solid red;
                width: 200px;
                height: 498px;
                float: left;
            }
            #product_bottom_right{
                border: 0px solid saddlebrown;
                width: 1094px;
                height: 498px;
                float: left;
            }
            #big{
                border: 0px solid hotpink;
                width: 545px;
                height: 247px;
                float: left;
            }
            .small{
                border: 0px solid blue;
                width: 180px;
                height: 247px;
                float: left;
                /*让里面的内容居中*/
                text-align: center;
            }
            #bottom{
                text-align: center;
            }
            /*去掉超链接的下划线*/
            a{
                text-decoration: none;
            }
        </style>
        
        <script>
            function init(){
                //书写轮播图显示的定时操作
                setInterval("changImg()",3000);
            }
            
            //书写函数
            var i=1;
            function changImg(){
                i++;
                
                //获取图片位置并设置src属性值
                document.getElementById("img_1").src="../img/"+i+".jpg";
                if(i==3){
                    i=0;
                }
            }
        </script>
    </head>
    <body body onload="init()">
        <div id="father">
            <!--1.logo部分-->
            <div id="logo">
                <div class="top">
                    <img src="../img/logo2.png" height="46px" />
                </div>
                <div class="top">
                    <img src="../img/header.png" height="46px"/>
                </div>
                <div class="top" id="top">
                    <a href="#">登录</a>
                    <a href="#">注册</a>
                    <a href="#">购物车</a>
                </div>
            </div>
                
            <!--2.导航栏部分-->    
            <div id="menu">
                <ul>
                    <a href="#"><li style="font-size: large;">首页</li></a>&nbsp;&nbsp;&nbsp;&nbsp;
                    <a href="#"><li>手机数码</li></a>&nbsp;&nbsp;&nbsp;&nbsp;
                    <a href="#"><li>家用电器</li></a>&nbsp;&nbsp;&nbsp;&nbsp;
                    <a href="#"><li>鞋靴箱包</li></a>&nbsp;&nbsp;&nbsp;&nbsp;
                </ul>
            </div>    
            
            <!--3.轮播图部分-->
            <div id="">
                <img src="../img/1.jpg" width="100%" height="100%" id="img_1"/>
            </div>
                
            <!--4.最新商品-->
            <div id="product">
                
                <div id="product_top">
                    <span style="font-size: 25px">最新商品</span>&nbsp;&nbsp;&nbsp;
                    <img src="../img/title2.jpg"/>
                </div>
                
                <div id="product_bottom">
                    
                    <div id="product_bottom_left">
                        <img src="../img/big01.jpg" width="100%" height="100%" />
                    </div>
                    
                    <div id="product_bottom_right">
                        <div id="big">
                            <a href="#"><img src="../img/middle01.jpg" width="100%" height="100%"  /></a>
                        </div>
                        
                        <div class="small">
                            <a href="#"><img src="../img/small01.jpg" ></a>
                            <a href="#"><p style="color: gray;">榨汁机</p></a>
                            <p style="color: red;">599</p>
                        </div>
                        <div class="small">
                            <a href="#"><img src="../img/small02.jpg" ></a>
                            <a href="#"><p style="color: gray;">电视机</p></a>
                            <p style="color: red;">1599</p>
                        </div>
                        <div class="small">
                            <a href="#"><img src="../img/small03.jpg" ></a>
                            <a href="#"><p style="color: gray;">锅</p></a>
                            <p style="color: red;">399</p>
                        </div>
                        <div class="small">
                            <a href="#"><img src="../img/small04.jpg" ></a>
                            <a href="#"><p style="color: gray;">面包机</p></a>
                            <p style="color: red;">799</p>
                        </div>
                        <div class="small">
                            <a href="#"><img src="../img/small05.jpg" ></a>
                            <a href="#"><p style="color: gray;">咖啡机</p></a>
                            <p style="color: red;">899</p>
                        </div>
                        <div class="small">
                            <a href="#"><img src="../img/small06.jpg" ></a>
                            <a href="#"><p style="color: gray;">洗衣机</p></a>
                            <p style="color: red;">999</p>
                        </div>
                        <div class="small">
                            <a href="#"><img src="../img/small07.jpg" ></a>
                            <a href="#"><p style="color: gray;">扫地机器人</p></a>
                            <p style="color: red;">1599</p>
                        </div>
                        <div class="small">
                            <a href="#"><img src="../img/small09.jpg" ></a>
                            <a href="#"><p style="color: gray;">微波炉</p></a>
                            <p style="color: red;">1099</p>
                        </div>
                        <div class="small">
                            <a href="#"><img src="../img/small08.jpg" ></a>
                            <a href="#"><p style="color: gray;">压力锅</p></a>
                            <p style="color: red;">799</p>
                        </div>
                    </div>
                </div>
            </div>
                
            <!--5.广告图片-->
            <div id="">
                <img src="../img/ad.jpg" width="100%"/>
            </div>
                
            <!--6.广告图片-->
            <div id="">
                <img src="../img/footer.jpg" width="100%"/>
            </div>
                
            <!--7.友情链接和版权信息-->
            <div id="bottom">
                    <a href="#"><font>关于我们</font></a>
                    <a href="#"><font>联系我们</font></a>
                    <a href="#"><font>招贤纳士</font></a>
                    <a href="#"><font>法律声明</font></a>
                    <a href="#"><font>友情链接</font></a>
                    <a href="#"><font>支付方式</font></a>
                    <a href="#"><font>配送方式</font></a>
                    <a href="#"><font>服务声明</font></a>
                    <a href="#"><font>广告声明</font></a>
                    <p>
                        Copyright © 2005-2016 hh商城 版权所有 
                    </p>
            </div>
        </div>
    </body>
</html>

在浏览器内运行,实现了轮播图的效果。

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