JavaScript连载33-点击查看大图效果以及闭包初步

一、点击图片显示大图代码

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>D33_1_SwitchIcon</title>
    <style>
        #box{
            border:1px solid #cccccc;
            width:360px;
            height:70px;
            padding-top:360px;
            margin:100px auto;
            background:url("img/img_05.png") no-repeat;
        }
        ul{
            display:flex;
            justify-content:center;
            align-items: center;
            cursor:pointer;
            list-style: none;
        }
        img{
            width: 250px;
        }
    </style>
</head>
<body>
    <div id="box">
        <ul>
            <li id="li01"><img src="img/img_01.png" alt=""></li>
            <li id="li02"><img src="img/img_02.png" alt=""></li>
            <li id="li03"><img src="img/img_03.png" alt=""></li>
            <li id="li04"><img src="img/img_04.png" alt=""></li>
            <li id="li05"><img src="img/img_05.png" alt=""></li>
        </ul>
    </div>
    <script>
        window.onload=function (ev) {
            //1.获取标签
            // var li01 = document.getElementById("li01");
            // var li02 = document.getElementById("li02");
            // var li03 = document.getElementById("li03");
            // var li04 = document.getElementById("li04");
            // var li05 = document.getElementById("li05");
            // var box = document.getElementById("box");
            //上面的语句我们使用函数来封装起来
            var li01 = $("li01");
            var li02 = $("li02");
            var li03 = $("li03");
            var li04 = $("li04");
            var li05 = $("li05");
            var box = $("box");
            //2.监听鼠标事件
            // li01.onmouseover = function (ev1) {
            //     box.style.background = 'url("img/img_01.png") no-repeat';
            // };
            // li02.onmouseover = function (ev2) {
            //     box.style.background = 'url("img/img_02.png") no-repeat';
            // };
            // li03.onmouseover = function (ev3) {
            //     box.style.background = 'url("img/img_03.png") no-repeat';
            // };
            // li04.onmouseover = function (ev4) {
            //     box.style.background = 'url("img/img_04.png") no-repeat';
            // };
            // li05.onmouseover = function (ev5) {
            //     box.style.background = 'url("img/img_05.png") no-repeat';
            // };
            li01.onmouseover = function (ev1) {
                changeImg("img/img_01.png")
            };
            li02.onmouseover = function (ev1) {
                changeImg("img/img_02.png")
            };
            li03.onmouseover = function (ev1) {
                changeImg("img/img_03.png")
            };
            li04.onmouseover = function (ev1) {
                changeImg("img/img_04.png")
            };
            li05.onmouseover = function (ev1) {
                changeImg("img/img_05.png")
            };
            //这样我们定义了鼠标的显示情况就可以来展示大图了
            //接下来我们封装函数，有大批量的重复代码

        }

        /**
         * 根据id获取标签
         * @param [string} id
         */
        function $(id) {   //$
            return typeof id === 'string'? document.getElementById(id):null;
        }

        /**
         *
         * @param {string}tag
         * @param {string}imgSrc
         */
        function changeImg(imgSrc) {
            box.style.background = 'url("'+ imgSrc + '") no-repeat';
        }

    </script>
</body>
</html>

二、如果使用闭包也可达到上面的效果

        window.onload = function (ev6) {
            //1.获取需要的标签
            var box = document.getElementById("box");
            var allList = box.getElementsByTagName("li");

            //2.监听鼠标进入li标签
            for(var i=0;i<allList.length;i++){
                //2.1取出单独的li标签
                var sLi = allList[i];
                // sLi.setAttribute("index",i+1);//复习设置属性的方法setAttribute
                // sLi.onmouseover = function (ev7) {
                //     console.log(this);
                //     console.log(this.getAttribute("index"));//获取这个li的index值
                // }
                //上面五行等价去下面,使用了闭包的知识，下次连载我们再讲
                (function (tag) {
                    sLi.onmouseover = function (ev9) {//复习onmouseover就是鼠标滑过这个模块之后要干的活儿
                        console.log(tag);
                        box.style.background =  'url("img/img_0'+ tag + '.png") no-repeat';
                    }
                })(i+1)
            }
        }

三、源码：

  • D33_1_SwitchIcon.html
  • D32_2_CommonMouse.html
  • D32_3_erweimaXianshi.html
  • 地址:https://github.com/ruigege66/JavaScript/blob/master/D33_1_SwitchIcon.html
  • https://github.com/ruigege66/JavaScript/blob/master/D32_2_CommonMouse.html
  • https://github.com/ruigege66/JavaScript/blob/master/D32_3_erweimaXianshi.html
  • 博客园：https://www.cnblogs.com/ruigege0000/
  • CSDN：https://blog.csdn.net/weixin_44630050?t=1
  • 欢迎关注微信公众号：傅里叶变换，个人账号，仅用于技术交流
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