一、浮动与定位复习

- 浮动与相对定位

```js
// 1.两者均参与布局
// 2.主浮动布局, 相对布局辅助完成布局微调
// 3.相对定位布局微调不同于盒模型布局微调, 相对定位布局不影响盒子原有位置, 就不会影响兄弟盒子布局
```

- 浮动与绝对定位

```js
// 1.只保留绝对定位布局
// 2.脱离文档流的盒子宽可以交于内容撑开
```

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>浮动与定位</title>
    <style>
        .box {
            /* 相对定位 */
            position: relative;
            /* 绝对定位 */
            position: absolute;
            /* 固定定位 */
            position: fixed;
        }
    </style>
    <style>
        ul {
            margin: 0;
            padding: 0;
            list-style: none;
        }
        li {
            float: left;
            cursor: pointer;
            border-bottom: 2px solid orange;
            /*padding: 0 5px;*/
            margin: 0 5px;
        }
        li:first-child {
            /*1.浮动与相对定位结合使用*/
            /*盒子采用的是浮动布局为主,
            相对定位可以辅助其子级绝对定位布局,
            也可以在浮动布局基础上微调
            */

            /*position: relative;*/
            /*采用相对定位布局, 在浮动布局基础上微调, 不影响兄弟盒子的布局*/
            /*left: 10px;*/
            /*采用盒模型布局, 在浮动布局基础上微调, 影响兄弟盒子的布局*/
            /*margin-left: 10px;*/
        }
        li {
            /*1.浮动与绝对定位结合使用*/
            /*盒子采用绝对定位布局,
            浮动布局失效
            */
            /*为什么: 因为两者都是脱离文档流, 绝对定位为完全脱离文档流*/
            position: absolute;
        }
        li:last-child {
            left: 100px;
        }
        /*脱离文档流: 盒子的宽度可以由内容撑开*/
        .ele {
            /* 100px;*/
            height: 100px;
            background-color: pink;
            /*float: right;*/
            position: absolute;
            right: 0;
        }
    </style>
</head>
<body>
    <!--布局: 1.盒模型布局 | 2.浮动布局 | 3.定位布局-->
    <ul>
        <li>列表项</li>
        <li>列表项</li>
        <li>列表项</li>
    </ul>
    <div class="ele">12345 67890</div>
</body>
</html>

二、小米菜单案例

- 默认活跃状态

```js
// 1.将初始的li设置一个active类名(拥有该类名就拥活跃状态表现的属性)
```

- 更改活跃状态

```js
let active_index = 0; // 活跃状态的索引
for (let i = 0; i < lis.length; i++) {
    lis[i].onmouseover = function () {
        // 清除之前活跃的
        lis[active_index].className = "";
        // 设置自身为活跃
        this.className = "active";
        // 更新活跃索引
        active_index = i;
    }
}
```

- 作用域(不同的js逻辑代码块)

```js
// 不要去使用全局变量, 不同的js逻辑代码块如果重复命名, 要么报重命名错误, 要么数据覆盖出现变量污染
// 每一个js逻辑代码块可以通过匿名函数的自调用完成局部作用域
(function(){
let a = 10;
})()
(function(){
let a = 20;
})()
```

- 根据数据与页面结构,动态渲染数据

```html
<ul class="main">
    <li>
        <a href="javascript:void(0)">
            <h2>小米音响</h2>
            <img src="https://i1.mifile.cn/a4/cf6660a3-d424-4248-889f-0eed1e99a342" alt="">
            <p>这是小米音响, 稍微解释一下</p>
        </a>
    </li>
    ...
</ul>
```

```js
let data = [
        [
            {
                title: "热门1",
                img_url: "https://i1.mifile.cn/a4/xmad_15435448534832_SAPDq.jpg",
                info: "这是热门"
            },
            ...还有三个{}
        ],
    ...还有三个[]
    ];
```

```js
let main_lis = document.querySelectorAll('.main li');
// 分析数据结构与页面结构,将指定数据渲染到指定位置
function updateData(index) {
    let dataArr = data[index];
    for (let i = 0; i < dataArr.length; i++) {
        let h2 = main_lis[i].querySelector('h2');
        h2.innerText = dataArr[i].title;
        let img = main_lis[i].querySelector('img');
        img.setAttribute('src', dataArr[i].img_url);
        let p = main_lis[i].querySelector('p');
        p.innerText = dataArr[i].info;
    }
}
```

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>小米菜单案例</title>
    <style>
        body, h2, ul {
            margin: 0;
            padding: 0;
        }
        ul {
            list-style: none;
        }
        a {
            color: black;
            text-decoration: none;
        }
        .title {
            background-color: #ddd;
            overflow: hidden;
            line-height: 60px;
        }
        .title h2 {
            float: left;
        }
        .title ul {
            float: right;
        }
        .title li {
            float: left;
            margin: 0 5px;
            line-height: 23px;
            margin-top: 20px;
            cursor: pointer;
        }
        .title li.active {
            color: #FF6700;
            border-bottom: 2px solid #FF6700;
            transition: .2s;
        }
    </style>
    <style>
        .main {
            overflow: hidden;
        }
        .main a {
            display: block;
            width: 300px;
            height: 400px;
            text-align: center;
        }
        .main li {
            float: left;
            width: 300px;
            height: 400px;
            background-color: orange;
            margin-right: 14px;
        }
        .main img {
            width: 260px;
        }
    </style>
</head>
<body>
    <div class="wrapper">
        <div class="title">
            <h2>搭配</h2>
            <ul>
                <li class="active">热门</li>
                <li>耳机音响</li>
                <li>电源</li>
                <li>电池与储蓄卡</li>
            </ul>
        </div>
        <ul class="main">
            <li>
                <a href="javascript:void(0)">
                    <h2>小米音响</h2>
                    <img src="https://i1.mifile.cn/a4/cf6660a3-d424-4248-889f-0eed1e99a342" alt="">
                    <p>这是小米音响, 稍微解释一下</p>
                </a>
            </li>
            <li>
                <a href="javascript:void(0)">
                    <h2>小米音响</h2>
                    <img src="https://i1.mifile.cn/a4/cf6660a3-d424-4248-889f-0eed1e99a342" alt="">
                    <p>这是小米音响, 稍微解释一下</p>
                </a>
            </li>
            <li>
                <a href="javascript:void(0)">
                    <h2>小米音响</h2>
                    <img src="https://i1.mifile.cn/a4/cf6660a3-d424-4248-889f-0eed1e99a342" alt="">
                    <p>这是小米音响, 稍微解释一下</p>
                </a>
            </li>
            <li>
                <a href="javascript:void(0)">
                    <h2>小米音响</h2>
                    <img src="https://i1.mifile.cn/a4/cf6660a3-d424-4248-889f-0eed1e99a342" alt="">
                    <p>这是小米音响, 稍微解释一下</p>
                </a>
            </li>
        </ul>
    </div>
</body>

<!--设置导航-->
<script>
(function () {
    // 制造数据(模拟后台请求得到的)
    let data = [
        [
            {
                title: "热门1",
                img_url: "https://i1.mifile.cn/a4/xmad_15435448534832_SAPDq.jpg",
                info: "这是热门"
            },
            {
                title: "热门2",
                img_url: "https://i1.mifile.cn/a4/xmad_15435448534832_SAPDq.jpg",
                info: "这是热门"
            },
            {
                title: "热门3",
                img_url: "https://i1.mifile.cn/a4/xmad_15435448534832_SAPDq.jpg1e99a342",
                info: "这是热门"
            },
            {
                title: "热门4",
                img_url: "https://i1.mifile.cn/a4/xmad_15435448534832_SAPDq.jpg",
                info: "这是热门"
            }
        ], [
            {
                title: "耳机1",
                img_url: "https://i1.mifile.cn/a4/xmad_14950995035103_fhWtH.jpg",
                info: "这是耳机"
            },
            {
                title: "耳机2",
                img_url: "https://i1.mifile.cn/a4/xmad_14950995035103_fhWtH.jpg",
                info: "这是耳机"
            },
            {
                title: "耳机3",
                img_url: "https://i1.mifile.cn/a4/xmad_14950995035103_fhWtH.jpg",
                info: "这是耳机"
            },
            {
                title: "耳机4",
                img_url: "https://i1.mifile.cn/a4/xmad_14950995035103_fhWtH.jpg",
                info: "这是耳机"
            }
        ], [], []
    ];

    let lis = document.querySelectorAll('.title li');
    // 设置一个记录活跃li索引的状态变量
    let active_index = 0;
    for (let i = 0; i < lis.length; i++) {
        lis[i].onmouseover = function () {
            // 清除之前活跃的
            lis[active_index].className = "";
            // 设置自身为活跃
            this.className = "active";
            // 更新活跃索引
            active_index = i;

            // 更新数据
            updateData(i);
        }
    }

    // 更新数据
    let main_lis = document.querySelectorAll('.main li');
    // 分析数据结构与页面结构,将指定数据渲染到指定位置
    function updateData(index) {
        let dataArr = data[index];
        // let count = 0;
        // for (dataObj of dataArr) {
        //     // console.log(dataObj.title);
        //     let h2 = main_lis[count].querySelector('h2');
        //     h2.innerText = dataObj.title;
        //     let img = main_lis[count].querySelector('img');
        //     img.setAttribute('src', dataObj.img_url);
        //     let p = main_lis[count].querySelector('p');
        //     p.innerText = dataObj.info;
        //     count++;
        // }
        for (let i = 0; i < dataArr.length; i++) {
            let h2 = main_lis[i].querySelector('h2');
            h2.innerText = dataArr[i].title;
            let img = main_lis[i].querySelector('img');
            img.setAttribute('src', dataArr[i].img_url);
            let p = main_lis[i].querySelector('p');
            p.innerText = dataArr[i].info;
        }
    }
    
})()
</script>

<!--完成数据更新-->
<script>
(function () {
    let lis = document.querySelectorAll('.main li');
})()
</script>

<!--
<script>
    var lis = document.querySelectorAll('.title li');
    for (let i = 0; i < lis.length; i++) {
        lis[i].onmouseover = function () {
            // 悬浮的li变成活跃状态, 之前活跃的li取消活跃状态

            // 移除所有的
            clearAllClassName()
            // 添加自己的
            this.className = "active"
        }
    }
    function clearAllClassName() {
        for (li of lis) {
            li.className = "";
        }
    }
</script>
-->

</html>

三、轮播图

```js
// 下一张
right_btn.onclick = function () {
    // 清除之前活跃的图片和tag
    img_lis[active_index].className = "";
    tag_lis[active_index].className = "";

    // 索引切换(更新活跃索引)
    // 安全性: 最后一张的下一张应该是第一张
    if (active_index == 4) active_index = -1;
    active_index++;

    // 设置将要活跃的图片和tag
    img_lis[active_index].className = "active";
    tag_lis[active_index].className = "active";
};
// active_index 记录了当前活跃状态的索引, 且所有逻辑共有
// 无限录播时考虑索引边界切换的问题
```

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>轮播图</title>
    <style >
        * {
            /*不允许选择文本, 网页文本不能负责*/
            user-select: none;
        }
        body, ul {
            margin: 0;
            padding: 0;
            list-style: none;
        }
        .scroll {
            width: 1226px;
            height: 460px;
            margin: 0 auto;
            background-color: orange;
            position: relative;
            cursor: pointer;
        }
        .scroll_view {
            width: 100%;
            height: 100%;
            position: relative;
        }
        .scroll_view li {
            background: red;
            width: 100%;
            height: 100%;
            font: normal 100px/460px 'STSong';
            text-align: center;
            position: absolute;
            top: 0;
            left: 0;
            opacity: 0;
        }
        .scroll_view li.active {
            opacity: 1;
            transition: .5s;
        }
        .left {
            position: absolute;
            top: 170px;
            left: 0;
            background-color: #eee;
            font-size: 100px;
        }
        .left:hover, .right:hover {
            cursor: pointer;
            background-color: #333;
        }
        .right {
            position: absolute;
            top: 170px;
            right: 0;
            background-color: #eee;
            font-size: 100px;
        }

        .scroll_tag {
            position: absolute;
            right: 10px;
            bottom: 10px;
        }
        .scroll_tag li {
            width: 10px;
            height: 10px;
            border-radius: 50%;
            background-color: #333;
            border: 3px solid #ddd;
            float: left;
            margin: 0 10px;
        }
        .scroll_tag li.active {
            background-color: #ccc;
            border: 3px solid #333;
        }
    </style>
</head>
<body>
<div class="scroll">
    <ul class="scroll_view">
        <li class="active">1</li>
        <li>2</li>
        <li>3</li>
        <li>4</li>
        <li>5</li>
    </ul>
    <ul class="scroll_toggle">
        <li class="left">&lt;</li>
        <li class="right">&gt;</li>
    </ul>
    <ul class="scroll_tag">
        <li class="active"></li>
        <li></li>
        <li></li>
        <li></li>
        <li></li>
    </ul>
</div>
</body>
<script>
(function () {
    let left_btn = document.querySelector('.left');
    let right_btn = document.querySelector('.right');
    let img_lis = document.querySelectorAll('.scroll_view li');
    let tag_lis = document.querySelectorAll('.scroll_tag li');
    let scroll = document.querySelector('.scroll');

    // 定时器
    let timer = 0;

    // 记录活跃状态的索引变量
    let active_index = 0;

    // 下一张
    right_btn.onclick = function () {
        // 清除之前活跃的图片和tag
        img_lis[active_index].className = "";
        tag_lis[active_index].className = "";

        // 索引切换(更新活跃索引)
        // 安全性: 最后一张的下一张应该是第一张
        if (active_index == 4) active_index = -1;
        active_index++;

        // 设置将要活跃的图片和tag
        img_lis[active_index].className = "active";
        tag_lis[active_index].className = "active";
    };
    // 上一张
    left_btn.onclick = function () {
        // 清除之前活跃的图片和tag
        img_lis[active_index].className = "";
        tag_lis[active_index].className = "";

        // 索引切换(更新活跃索引)
        // 安全性: 第一张的前一张应该是最后一张
        if (active_index == 0) active_index = 5;
        active_index--;

        // 设置将要活跃的图片和tag
        img_lis[active_index].className = "active";
        tag_lis[active_index].className = "active";
    };

    // 自动轮播
    function autoScroll() {
        timer = setInterval(function () {
            // 清除之前活跃的图片和tag
            img_lis[active_index].className = "";
            tag_lis[active_index].className = "";

            // 索引切换(更新活跃索引)
            // 安全性: 最后一张的下一张应该是第一张
            if (active_index == 4) active_index = -1;
            active_index++;

            // 设置将要活跃的图片和tag
            img_lis[active_index].className = "active";
            tag_lis[active_index].className = "active";
        }, 1500);
    }
    // 加载页面就只执行一次,打开自动轮播
    autoScroll();

    // 鼠标悬浮轮播图停止自动轮播
    scroll.onmouseenter = function () {
        clearInterval(timer)
    };
    // 鼠标移开重新开启自动轮播
    scroll.onmouseleave = function () {
        autoScroll();
    };

    // tag点击对应的图片切换
    for (let i = 0; i < tag_lis.length; i++) {
        tag_lis[i].onclick = function () {
            // console.log(i);
            // 清除之前活跃的图片和tag
            img_lis[active_index].className = "";
            tag_lis[active_index].className = "";

            // 更新活跃索引
            active_index = i;

            // 设置将要活跃的图片和tag
            img_lis[active_index].className = "active";
            tag_lis[active_index].className = "active";
        }
    }

})()
</script>
</html>

四、滚动轮播

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>滚动轮播</title>
    <style>
        body, ul {
            margin: 0;
            padding: 0;
            list-style: none;
            user-select: none;
        }

        .wrapper {
            width: 400px;
            height: 240px;
            background-color: orange;
            margin: 50px auto;
            position: relative;
            overflow: hidden;
        }
        /* 滚得的标签是ul, 带动着4个li同步运动 */
        .scroll_view {
            width: 1600px;
            /*利用绝对定位完成运动*/
            position: absolute;
            top: 0;
            /*left: -400px;*/
            left: 0;
            /*transition: 1s;*/
        }
        .scroll_view li {
            width: 400px;
            height: 240px;
            font: normal 80px/240px 'STSong';
            text-align: center;
            float: left;
        }
        .li1 { background-color: pink }
        .li2 { background-color: deeppink }
        .li3 { background-color: lightpink }
        .li4 { background-color: hotpink}

        .left {
            position: absolute;
            top: 100px;
            left: 0;
            background-color: #eee;
            font-size: 30px;
        }
        .left:hover, .right:hover {
            cursor: pointer;
            background-color: #333;
        }
        .right {
            position: absolute;
            top: 100px;
            right: 0;
            background-color: #eee;
            font-size: 30px;
        }

        .scroll_tag {
            position: absolute;
            right: 10px;
            bottom: 10px;
        }
        .scroll_tag li {
            width: 10px;
            height: 10px;
            border-radius: 50%;
            background-color: #333;
            border: 3px solid #ddd;
            float: left;
            margin: 0 10px;
        }
        .scroll_tag li.active {
            background-color: #ccc;
            border: 3px solid #333;
        }
    </style>
</head>
<body>
    <div class="wrapper">
        <ul class="scroll_view">
            <li class="li1">1</li>
            <li class="li2">2</li>
            <li class="li3">3</li>
            <li class="li4">4</li>
        </ul>
        <ul class="scroll_toggle">
            <li class="left">&lt;</li>
            <li class="right">&gt;</li>
        </ul>
        <ul class="scroll_tag">
            <li class="active"></li>
            <li></li>
            <li></li>
            <li></li>
        </ul>
    </div>
</body>
<script>
(function () {
    let scroll_view = document.querySelector('.scroll_view');
    let left_btn = document.querySelector('.left');
    let right_btn = document.querySelector('.right');
    let tag_lis = document.querySelectorAll('.scroll_tag li');
    
    right_btn.onclick = function () {
        let total_lenth = 400;
        let count = 0;
        let step = 8;
        let timer = setInterval(function () {
            // 通过滚动的距离映射出所在的图片索引
            let index = parseInt(-scroll_view.offsetLeft / total_lenth);
            index += 1;
            console.log(index);
            // 临界点, 往右4
            if (index == 4) {
                clearInterval(timer);
                return;
            }

            // 0+1 ==> 1
            // 1+1 ==> 2
            // 2+1 ==> 3
            tag_lis[index - 1].className = "";
            tag_lis[index].className = "active";

            scroll_view.style.left = scroll_view.offsetLeft - step + 'px';
            count++;
            if (count >= total_lenth / step) {
                clearInterval(timer)
            }
        }, 10);
    };

    left_btn.onclick = function () {
        let total_lenth = 400;
        let count = 0;
        let step = 8;
        let timer = setInterval(function () {
            // 要偏移坐标系, 要加上一个宽度400 total_lenth
            // 要处理第一次偏移bug, 少加上8 step
            let index = parseInt((-scroll_view.offsetLeft + 392) / total_lenth);
            console.log(index);
            // 处理第一次偏移bug

            // 3 => 2
            // 2 => 1
            // 1 => 0
            // 临界点, 往左0
            if (index == 0) {
                clearInterval(timer);
                return;
            }
            // if (index == 4) index = 3;
            tag_lis[index].className = "";
            tag_lis[index - 1].className = "active";

            scroll_view.style.left = scroll_view.offsetLeft + step + 'px';
            count++;
            if (count >= total_lenth / step) {
                clearInterval(timer)
            }
        }, 10);
    }
})()
</script>
</html>