<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        * {
            margin: 0;
            padding: 0;
            list-style: none;
        }

        .box {
            position: relative;
            width: 100vw;
            height: 100vh;
            overflow: hidden;
        }

        .fullpage {
            position: absolute;
            top: 0;
            left: 0;
        }

        section {
            width: 100vw;
            height: 100vh;
            font-size: 80px;
            display: flex;
            justify-content: center;
            align-items: center;
            color: #fff;
        }

        .section_1 {
            background-color: aqua;
        }

        .section_2 {
            background-color: skyblue;
        }

        .section_3 {
            background-color: darksalmon;
        }

        .section_4 {
            background-color: red;
        }

        .section_5 {
            background-color: forestgreen;
        }

        ul {
            position: absolute;
            right: 20px;
            top: 50%;
            transform: translateY(-50%);
            width: 18px;
            /* height: 100px; */
            border-radius: 5px;
            background-color: rgba(255, 255, 255, .7);
            display: flex;
            flex-wrap: wrap;
            align-items: center;
            justify-content: center;
        }

        ul li {
            width: 10px;
            height: 10px;
            border-radius: 50%;
            background-color: skyblue;
        }

        ul .active {
            background-color: red;
        }
    </style>
</head>

<body>
    <div class="box">
        <div class="fullpage">
            <section class="section_1">
                有在好好生活
            </section>
            <section class="section_2">
                过程用心 结果随缘
            </section>
            <section class="section_3">
                家人闲坐 灯火可亲
            </section>
            <section class="section_4">
                我将归来 万马千军
            </section>
            <section class="section_5">
                放弃一定不难 但坚持很酷
            </section>
        </div>

        <!-- 小圆点 -->
        <ul>
            <!-- <li class="active"></li>
            <li></li>
            <li></li>
            <li></li>
            <li></li> -->
        </ul>
    </div>
    <script src="../tools.js"></script>
    <script>
        // 获取元素
        const wrap = document.querySelector('.fullpage');
        const sections = document.querySelectorAll('section');
        const ul = document.querySelector('ul')
        // 动态设置小圆点 
        for (let i = 0; i < sections.length; i++) {
            var li = document.createElement('li')
            if (i == 0) {
                li.classList.add('active');
            }
            ul.appendChild(li)
        }
        // 动态设置小圆点父盒子的宽  ul
        ul.style.height = li.offsetHeight * ul.children.length * 2 + 'px'

        // 给wrap设置一个动态高度
        wrap.style.height = sections.length * wrap.firstElementChild.offsetHeight + 'px'
        // 获取滚动条的高度  让鼠标滚动一视口的高
        // 视口高的索引
        var index = 0
        // 获取浏览器的视口高
        var wh = window.innerHeight
        // 为了防止动画未完成 点击过快造成的抖动 而加锁
        var flag = true
        // 添加一个鼠标滚轮事件
        window.onmousewheel = function (e) {
            if (!flag) {
                return
            }
            flag = false
            // var e = window.event || e
            if (e.deltaY > 0) {
                index++
                // deltaY 大于0是 向下
                if (index > sections.length - 1) {
                    index = sections.length - 1
                }
                move(wrap, {
                    top: -index * wh
                }, function () {
                    // 动画完成后在执行小圆点跟随  
                    // 让小圆点随着屏的变动而变动
                    for (let i = 0; i < ul.children.length; i++) {
                        ul.children[i].classList.remove('active');
                    }
                    ul.children[index].classList.add('active')
                    flag = true
                })
            } else {
                index--;
                if (index < 0) {
                    index = 0
                }
                move(wrap, {
                    top: -index * wh
                }, function () {
                    // 动画完成后在执行小圆点跟随  
                    // 让小圆点随着屏的变动而变动
                    for (let i = 0; i < ul.children.length; i++) {
                        ul.children[i].classList.remove('active');
                    }
                    ul.children[index].classList.add('active')
                    flag = true
                })
            }
        }

        // 点击小圆点
        for (let i = 0; i < ul.children.length; i++) {
            ul.children.onclick = function () {
                if (!flag) {
                    return
                }
                flag = false
                index = i;
                move(wrap, {
                    top: -index * wh
                }, function () {
                    // 动画完成后在执行小圆点跟随  
                    // 让小圆点随着屏的变动而变动
                    for (let i = 0; i < ul.children.length; i++) {
                        ul.children[i].classList.remove('active');
                    }
                    ul.children[index].classList.add('active')
                    flag = true
                })
            }
        }
 
/* 
封装获取样式的函数 
@ ele 元素
@ attr 属性
*/
function getStyle(ele,attr) {
    if (window.getComputedStyle) {
       return parseInt(window.getComputedStyle(ele)[attr])
    } else {
        // 因为attr是个变量不是一个字符串 所以不能直接 .键  要用[]
       return parseInt(ele.currentStyle[attr])
    }
}
 
 /*    
     运动封装方法
      @ele  运动的元素
     @aObj 对象 key是运动的属性  value是运动的目标值(终点)
     @cb是一个回调函数 
 */
     function move(ele, aObj, cb) {
        var obj = {}
        for (let attr in aObj) {
            obj[attr] = setInterval(() => {
                // 要获取动态的当前位置
                let oldStyle = getStyle(ele, attr)
                let step = (aObj[attr] - oldStyle) / 10;
                // 判断step为正负?
                step > 0 ? step = Math.ceil(step) : step = Math.floor(step)
                // 判断是否走到目标位置
                if (oldStyle === aObj[attr]) {
                    clearInterval(obj[attr])
                    delete obj[attr];
                    if (isEmptyObj(obj)) {
                        // 对象为空 动画结束
                        cb() // 使用则个函数
                    }
                } else {
                    // 没走到目标位置
                    ele.style[attr] = oldStyle + step + 'px'
                }
            }, 30);
        }
    }
 
// 3.通过ES6新增的一个Object.keys()方法
    function isEmptyObj(obj) {
        if (Object.keys(obj).length == 0) {
            return true;
        } else {
            return false;
        }
    }
    </script>
</body>

</html>