老师,滚动滚动条时,每个屏幕都没有动画效果,然后导航栏也没有一直在顶部是怎么回事

老师,滚动滚动条时,每个屏幕都没有动画效果,然后导航栏也没有一直在顶部是怎么回事

代码顺序为:index.html、index.js、test.js、animate.css、index.css,麻烦老师帮忙看看哪里出了问题

<!DOCTYPE html>
<html>
<head>
	<title>个人网页</title>
	<link rel="stylesheet" type="text/css" href="css/base.css">
	<link rel="stylesheet" type="text/css" href="css/index.css">
	<link rel="stylesheet" type="text/css" href="css/animate.css">
</head>
<body>
	<!-- 头部 -->
	<header class="header">
		<div class="header__wrap">
			<div class="header__logo">慕课手机</div>
			<nav class="header__nav">
			<!-- 点击不会有触发 -->
			<a href="javascript:;" class="header__nav-item header__nav-item_status_active">首页</a>
			<a href="javascript:;" class="header__nav-item">外观</a>
			<a href="javascript:;" class="header__nav-item">配置</a>
			<a href="javascript:;" class="header__nav-item">型号</a>
			<a href="javascript:;" class="header__nav-item">说明</a>
			<a href="javascript:;" class="header__nav-item header__nav-item_custom_button">立即购买</a>
		</nav>
		</div>
	</header>
	<!-- 第一屏 -->
	<div class="screen-1">
		<!-- 文字 -->
		<h2 class="screen-1__heading"><b>慕课手机</b>让你的生活更精彩</h2>
		<!-- 手机 -->
		<div class="screen-1__phone"></div>
		<!-- 阴影 -->
		<div class="screen-1__shadow"></div>
	</div>
	<!-- 第二屏 -->
	<div class="screen-2">
		<!-- 文字 -->
		<h2 class="screen-2__heading">优美的设计,更令人着迷</h2>
		<h3 class="screen-2__subheading">采用最受欢迎的设计,让它更加出色。<br/>款式小巧、轻便手感更舒适。绚丽高清的显示屏,整个外观显得格外精致。</h3>
		<!-- 手机 -->
		<div class="screen-2__phone">
			<div class="screen-2__point screen-2__point_i_1">高清摄像</div>
			<div class="screen-2__point screen-2__point_custom_right screen-2__point_i_2">超薄机身</div>
			<div class="screen-2__point screen-2__point_custom_right screen-2__point_i_3">大屏显示</div>
		</div>
	</div>
	<!-- 第三屏 -->
	<div class="screen-3">
		<div class="screen-3__wrap">
			<!-- 文字 -->
			<h2 class="screen-3__heading">外形小巧,功能强大的手机</h2>
			<h3 class="screen-3__subheading">采用最受欢迎的设计,让它更加出色。<br/>款式小巧、轻便手感更舒适。绚丽高清的显示屏,整个外观显得格外精致。</h3>
			<!-- 手机 -->
			<div class="screen-3__phone"></div>
			<div class="screen-3__features">
				<div class="screen-3__features__item">
					<div class="screen-3__features__item__number">5.7</div>
					<div class="screen-3__features__item__desc">英寸大屏</div>
				</div>
				<div class="screen-3__features__item">
					<div class="screen-3__features__item__number">1200</div>
					<div class="screen-3__features__item__desc">万像素</div>
				</div>
				<div class="screen-3__features__item">
					<div class="screen-3__features__item__number">3D</div>
					<div class="screen-3__features__item__desc">touch</div>
				</div>
				<div class="screen-3__features__item">
					<div class="screen-3__features__item__number">A9</div>
					<div class="screen-3__features__item__desc">处理器</div>
				</div>
			</div>
		</div>
	</div>
	<!-- 第四屏 -->
	<div class="screen-4">
		<div class="screen-4__wrap">
			<!-- 文字 -->
			<h2 class="screen-4__heading">丰富的手机型号</h2>
			<h3 class="screen-4__subheading">找到适合你的手机</h3>

			<div class="screen-4__type">
				<div class="screen-4__type__item screen-4__type__item_i_1">
					<div class="screen-4__type__item__color">慕课红</div>
					<div class="screen-4__type__item__storage">16G/32G/64G</div>
				</div>

				<div class="screen-4__type__item screen-4__type__item_i_2">
					<div class="screen-4__type__item__color">土豪金</div>
					<div class="screen-4__type__item__storage">16G/32G/64G</div>
				</div>

				<div class="screen-4__type__item screen-4__type__item_i_3">
					<div class="screen-4__type__item__color">太空灰</div>
					<div class="screen-4__type__item__storage">16G/32G/64G</div>
				</div>

				<div class="screen-4__type__item screen-4__type__item_i_4">
					<div class="screen-4__type__item__color">绅士黑</div>
					<div class="screen-4__type__item__storage">16G/32G/64G</div>
				</div>
			</div>
		</div>
	</div>
	<!-- 第五屏 -->
	<div class="screen-5">
			<!-- 文字 -->
			<h2 class="screen-5__heading">游戏、学习、拍照、有这一部就够了</h2>
			<h3 class="screen-5__subheading">看视频、拍摄高清视频与照片、视频聊天、一机多功能,让您的生活更丰富精彩</h3>
			<div class="screen-5__bg"></div>
	</div>
	<div class="screen-buy">
		<a class="screen-buy__button" href="javascript:;">立即购买</a>
	</div>
	<!-- 底部 -->
	<footer class="footer">
		© 2016 imooc.com   京ICP备13046642号
	</footer>
	<!-- 导航侧边栏 -->
	<div class="outline">
		<a href="javascript:;" class="outline__item outline__item_status_active">首页</a>
		<a href="javascript:;" class="outline__item">外观</a>
		<a href="javascript:;" class="outline__item">配置</a>
		<a href="javascript:;" class="outline__item">型号</a>
		<a href="javascript:;" class="outline__item">说明</a>
	</div>
	<script type="text/javascript" src="js/test.js"></script>
	<script type="text/javascript" src="js/index.js"></script>
</body>
</html>
//获取元素
var getElem = function(selector){
	return document.querySelector(selector);
}

var getAllElem = function(selector){
	return document.querySelector(selector);
}

// 获取元素样式
var getCls = function(element){
	return element.getAttribute('class');
}
// 设置元素样式
var setCls = function(element , cls){
	return element.setAttribute('class' , cls);
}
// 为元素添加样式
var addCls = function(element , cls){
	var baseCls = getCls(element);
	// 如果没有找到这个样式,就加一个
	if( baseCls.indexOf(cls) === -1){
		setCls( element , baseCls+' '+cls);
	}
}
// 为元素删除样式
var delCls = function(element , cls){
	var baseCls = getCls(element);
	//如果能找到这个样式,就删除
	if( baseCls.indexOf(cls) != -1){
		setCls( element , baseCls.split(cls).join(' ') .replace(/\s+/g,' '));
	}
}
// 页面载入完成后,所有动画元素设置_animate_init
// 第一步:初始化样式 init
var screenAnimateElements = {
	// 每屏动画
	'.screen-1' : [
		'.screen-1__heading',
		'.screen-1__phone',
		'.screen-1__shadow',
	],
	'.screen-2' : [
		'.screen-2__heading',
		'.screen-2__subheading',
		'.screen-2__phone',
		'.screen-2__point_i_1',
		'.screen-2__point_i_2',
		'.screen-2__point_i_3',
	],
	'.screen-3' : [
		'.screen-3__heading',
		'.screen-3__phone',
		'.screen-3__subheading',
		'.screen-3__features',
	],
	'.screen-4' : [
		'.screen-4__heading',
		'.screen-4__subheading',
		'.screen-4__type__item_i_1',
		'.screen-4__type__item_i_2',
		'.screen-4__type__item_i_3',
		'.screen-4__type__item_i_4',
	],
	'.screen-5' : [
		'.screen-5__heading',
		'.screen-5__subheading',
		'.screen-5__bg',
	],
};
// 把某个屏幕上有动画样式的都设为init
//设置屏内元素为初始状态
var setScreenAnimateInit = function(screenCls){
	var screen = document.querySelector(screenCls);//获取当前屏的元素
	var animateElements = screenAnimateElements[screenCls];//需要设置动画的元素
	for(var i=0; i<animateElements.length; i++){
		var element = document.querySelector(animateElements[i]);
		var baseCls = element.getAttribute('class');
		element.setAttribute('class',baseCls +' '+animateElements[i].substr(1)+'_animate_init');
	}
}
// 设置播放屏内的元素动画
var playScreenAnimateDone = function(screenCls){
	var screen = document.querySelector(screenCls);//获取当前屏的元素
	var animateElements = screenAnimateElements[screenCls];//需要设置动画的元素
	for(var i=0; i<animateElements.length; i++){
		var element = document.querySelector(animateElements[i]);
		var baseCls = element.getAttribute('class');
		element.setAttribute('class',baseCls.replace('_animate_init','_animate_done'));
	}
}
window.onload = function(){
	console.log('onload');
	// 每一屏动画
	for(k in screenAnimateElements){
		setScreenAnimateInit(k);
	}
}
// 第二步:滚动到哪里,就播放到哪里
window.onscroll = function(){
	var top = document.body.scrollTop;
	console.log(top);
	if(top > 80){
		addCls(getElem('.header') , 'header_status_back');
	}else{
		delCls(getElem('.header') , 'header_status_back');
	}

	// 滚动条大于800时要让第一屏播放
	if(top > 1){
		playScreenAnimateDone('.screen-1');
	}
	if(top > 800*1){
		playScreenAnimateDone('.screen-2');
	}
	if(top > 800*2){
		playScreenAnimateDone('.screen-3');
	}
	if(top > 800*3){
		playScreenAnimateDone('.screen-4');
	}
	if(top > 800*4){
		playScreenAnimateDone('.screen-5');
	}
}
// 将有动画效果的放一起
var screenAnimateElements = {
	// 每屏动画
	'.screen-1' : [
		'.screen-1__heading',
		'.screen-1__phone',
		'.screen-1__shadow',
	],
	'.screen-2' : [
		'.screen-2__heading',
		'.screen-2__subheading',
		'.screen-2__phone',
		'.screen-2__point_i_1',
		'.screen-2__point_i_2',
		'.screen-2__point_i_3',
	],
	'.screen-3' : [
		'.screen-3__heading',
		'.screen-3__phone',
		'.screen-3__subheading',
		'.screen-3__features',
	],
	'.screen-4' : [
		'.screen-4__heading',
		'.screen-4__subheading',
		'.screen-4__type__item_i_1',
		'.screen-4__type__item_i_2',
		'.screen-4__type__item_i_3',
		'.screen-4__type__item_i_4',
	],
	'.screen-5' : [
		'.screen-5__heading',
		'.screen-5__subheading',
		'.screen-5__bg',
	],
};


// 设置当前屏幕的样式
function setScreenAnimate(screenCls){
	var screen = document.querySelector(screenCls);//获取当前屏的元素
	var animateElements = screenAnimateElements[screenCls];//需要设置动画的元素
	//测试是否有初始化子元素的样式
	var isSetAnimateClass = false;
	//当前屏幕下所有子元素的状态是DONE?
	var isAnimateDone = false;
	screen.onclick = function(){
		// 初始化样式,增加init(A A_init)
		if( isSetAnimateClass === false){
			for(var i=0; i<animateElements.length; i++){
				var element = document.querySelector(animateElements[i]);
				var baseCls = element.getAttribute('class');
				element.setAttribute('class',baseCls +' '+animateElements[i].substr(1)+'_animate_init');
			}
			isSetAnimateClass = true;
			return ;
		}
		//切换所有的 AnimateElements 的 init ——> done (A A_done)
		if( isAnimateDone === false){
			for(var i=0; i<animateElements.length; i++){
				var element = document.querySelector(animateElements[i]);
				var baseCls = element.getAttribute('class');
				element.setAttribute('class',baseCls.replace('_animate_init','_animate_done'));
			}
			isAnimateDone = true;
			return ;
		}
		//切换所有的 AnimateElements 的 done ——> init (A A_init)
		if( isAnimateDone === true){
			for(var i=0; i<animateElements.length; i++){
				var element = document.querySelector(animateElements[i]);
				var baseCls = element.getAttribute('class');
				element.setAttribute('class',baseCls.replace('_animate_done','_animate_init'));
			}
			isAnimateDone = false;
			return ;
		}
	}
}
// 每一屏动画
for(k in screenAnimateElements){
	setScreenAnimate(k);
}
/*第一屏文字内容*/
/*第一屏文字*/
.screen-1__shadow,
.screen-1__phone,
.screen-1__heading{
	transition: all 1s;
}
.screen-1__heading_animate_init{
	opacity: 0;
	transform: translate(0,100%);
}
.screen-1__shadow_animate_done,
.screen-1__phone_animate_done,
.screen-1__heading_animate_done{
	opacity: 1;
	transform: translate(0,0);
}
/*第一屏手机*/
.screen-1__phone_animate_init{
	opacity: 0;
	transform: translate(0,-100%);
}
/*第一屏手机阴影*/
.screen-1__shadow_animate_init{
	opacity: 0;
	transform: translate(0,100%);
}

/*第二屏动画*/
.screen-2__subheading,
.screen-2__phone,
.screen-2__heading{
	transition: all 1s;
}
.screen-2__heading_animate_init{
	opacity: 0;
	transform: translate(0,-100%);
}
.screen-2__subheading_animate_init{
	opacity: 0;
	transform: translate(0,100%);
}
.screen-2__phone_animate_init{
	opacity: 0;
	transform: translate(0,50%);
}
.screen-2__phone_animate_done,
.screen-2__subheading_animate_done,
.screen-2__heading_animate_done{
	opacity: 1;
	transform: translate(0,0);
}
.screen-2__point{
	transition: all 1s 1s;
}
.screen-2__point_done{
	opacity: 1;
	transform: translate(0,0);
}
.screen-2__point_i_1_animate_init{
	opacity: 0;
	transform: translate(-100%,0);
}
.screen-2__point_i_3_animate_init,
.screen-2__point_i_2_animate_init{
	opacity: 0;
	transform: translate(100%,0);
}
/*第三屏动画*/
.screen-3__features,
.screen-3__subheading,
.screen-3__phone,
.screen-3__heading{
	transition: all 1s;
}
.screen-3__phone_animate_done,
.screen-3__subheading_animate_done,
.screen-3__heading_animate_done{
	opacity: 1;
	transform: translate(0,0);
}

.screen-3__heading_animate_init{
	opacity: 0;
	transform: translate(0,-100%);
}
.screen-3__phone_animate_init,
.screen-3__subheading_animate_init{
	opacity: 0;
	transform: translate(0,100%);
}
.screen-3__features_animate_init{
	opacity: 0;
	transform: scale(.5);
}
.screen-3__features_animate_done{
	opacity: 1;
	transform: scale(1);
}
.screen-3__features__item{
	transition: all .5s;
	cursor: pointer;
}
.screen-3__features__item:hover{
	transform: scale(1.1);
	border-color: #fff;
}
/*第四屏动画*/
.screen-4__subheading,
.screen-4__heading{
	transition: all 1s;
}
.screen-4__heading_animate_init{
	opacity: 0;
	transform: translate(0,-100%);
}
.screen-4__subheading_animate_init{
	opacity: 0;
	transform: translate(0,100%);
}
.screen-4__type__item_i_1{
	transition: all 1s .5s;
}
.screen-4__type__item_i_2{
	transition: all 1s 1s;
}
.screen-4__type__item_i_3{
	transition: all 1s 1.5s;
}
.screen-4__type__item_i_4{
	transition: all 1s 2s;
}

.screen-4__type__item_i_1_animate_init,
.screen-4__type__item_i_2_animate_init,
.screen-4__type__item_i_3_animate_init,
.screen-4__type__item_i_4_animate_init{
	opacity: 0;
}
.screen-4__type__item_i_1_animate_done,
.screen-4__type__item_i_2_animate_done,
.screen-4__type__item_i_3_animate_done,
.screen-4__type__item_i_4_animate_done{
	opacity: 1;
}
/*第五屏动画*/
.screen-5__bg,
.screen-5__subheading,
.screen-5__heading{
	transition: all 1s;
}
.screen-5__heading_animate_init{
	opacity: 0;
	transform: translate(0,-100%);
}
.screen-5__bg_animate_init,
.screen-5__subheading_animate_init{
	opacity: 0;
	transform: translate(0,100%);
}


/*定义帧动画*/
@-webkit-keyframes bounce {
	0%,100% {
		transform: scale(0);
	}
	50% {
		transform: scale(1);
	}
}
/*给第二屏的手机介绍使用帧动画*/
.screen-2__point:before,
.screen-2__point:after{
	content: ' ';
	display: block;
	width: 20px;
	height: 20px;
	position: absolute;
	top: 1px;
	left: 0px;
	background-color: rgba(255,0,0,0.4);
	border-radius: 50%;
	-webkit-animation: bounce 2s infinite;
}

.screen-2__point:before{
	-webkit-animation: bounce 2s infinite 1s;
}
.screen-2__point_i_1:after,
.screen-2__point_i_1:before{
	left: 200px;
}
/*导航条 _status_back 样式*/
.header{
	transition: all 1s;
}
.header_status_back{
	background-color: rgba(0,0,0,.5);
	position: fixed;
	top: 0;
	left: 0;
	right: 0;
	z-index: 3;
}
.header_status_back .header__logo,
.header_status_back .header__nav-item{
	color: #fff;
}
/*
BEM设计模式
模块(没有前缀,多个单词用“-”连接)
元素(元素在模块之后,可以有多个层级,以__连接)
修饰(某元素、或某模块特别的状态,必须有一个状态名和状态值,使用_连接)
*/
/*头部*/
.header{
	background-color: #f7f7f7;
}
/*包含内容*/
.header__wrap{
	height: 80px;
	width: 1200px;
	position: relative;
	margin: 0 auto;
}
/*logo*/
.header__logo{
	width: 100px;
	height: 38px;
	line-height: 38px;
	font-size: 20px;
	color: #07111b;
	padding-left: 50px;
	background:url('../img/logo.png') left center no-repeat;
	background-size: 38px 38px;
	position: absolute;
	top:50%;
	margin-top: -19px;
	left: 20px;
}
/*导航*/
.header__nav{
	position: absolute;
	right: 20px;
	height: 38px;
	top: 50%;
	margin-top: -19px;
}
/*导航内元素*/
.header__nav-item{
	color: #292f35;
	font-size: 14px;
	display: block;
	height: 38px;
	line-height: 38px;
	float: left;
	margin-left: 40px;
	position: relative;
}
/*鼠标移入导航文字变红*/
.header__nav-item:hover{
	color: #f01400;
}
/*状态与状态值*/
.header__nav-item_status_active{
	color: #f01400;
}
/*导航的下划线*/
.header__nav-item_status_active::after{
	content:' ';
	display: block;
	width: 100%;
	height: 2px;
	position: absolute;
	background-color: #f01400;
	left: 0;
	bottom: 0;
}
/*导航条上的按钮*/
.header__nav-item_custom_button{
	background: #000;
	color: #f4f4f5;
	text-align: center;
	width: 90px;
	border-radius: 3px;
}
/*第一屏*/
.screen-1{
	height: 800px;
	background-color: #e7e7e7;
	background:url(../img/bg-screen-1.png) no-repeat center;
	position: relative;
	overflow: hidden;
	background:url(../img/bg-screen-1.png) no-repeat center;
	/*让背景图撑满整个屏*/
	background-size: cover;
}
/*文字内容*/
.screen-1__heading{
	font-weight: normal;
	margin:0;
	padding: 0;
	font-size: 46px;
	color: #4d555d;
	text-align: center;
	padding-top: 152px;
}
.screen-1__heading b{
	color: #f01400;
	font-weight: normal;
}
/*手机*/
.screen-1__phone{
	width: 1375px;
	height: 305px;
	background:url(../img/screen-1-phone.png) no-repeat center;
	position: absolute;
	left: 50%;
	margin-left: -687px;
	bottom: 180px;
	z-index: 2;
}
/*阴影*/
.screen-1__shadow{
	width: 1233px;
	height: 411px;
	background:url(../img/screen-1-shadow.png) no-repeat center;
	position: absolute;
	left: 50%;
	margin-left: -616px;
	bottom: 30px;
	z-index: 1;
	opacity: .8;
}
/*第二屏*/
.screen-2{
	height: 800px;
	background-color: #fafafa;
	position: relative;
	overflow: hidden;
}
/*大标题*/
.screen-2__heading{
	font-weight: normal;
	margin:0;
	padding: 0;
	font-size: 46px;
	line-height: 46px;
	color: #f01400;
	text-align: center;
	padding-top: 96px;
}
/*子标题*/
.screen-2__subheading{
	font-weight: normal;
	margin:0;
	padding: 0;
	font-size: 14px;
	color: #2c3137;
	text-align: center;
	padding-top: 25px;
	line-height: 28px;
}
/*手机*/
.screen-2__phone{
	width: 928px;
	height: 873px;
	background:url(../img/screen-2-phone.png) no-repeat center;
	position: absolute;
	left: 50%;
	margin-left: -464px;
	bottom: -345px;
	z-index: 2;
}
/*手机描述*/
.screen-2__point{
	width: 108px;
	height: 22px;
	padding-right: 112px;
	font-size: 22px;
	line-height: 22px;
	color: #4d555d;
	position: absolute;
	background:url(../img/icon-point-right.png) no-repeat center right;
}
.screen-2__point_custom_right{
	padding:0 0 0 112px;
	background:url(../img/icon-point-left.png) no-repeat center left;
}
/*手机描述位置*/
.screen-2__point_i_1{
	top: 150px;
	left: -164px;
}
.screen-2__point_i_2{
	top: 30px;
	right: 130px;
}
.screen-2__point_i_3{
	top: 330px;
	right: 30px;
}
/*第三屏*/
.screen-3{
	height: 800px;
	background-color: red;
	position: relative;
	overflow: hidden;
	background:url(../img/bg-screen-3.png) no-repeat center;
	/*让背景图撑满整个屏*/
	background-size: cover;
}
/*第三屏容器*/
.screen-3__wrap{
	width: 1200px;
	height: auto;
	margin: 0 auto;
	position: relative;
}
/*大标题*/
.screen-3__heading{
	font-size: 46px;
	line-height: 46px;
	color: #fff;
	text-align: left;
	padding-top: 94px;
}
/*子标题*/
.screen-3__subheading{
	font-size: 14px;
	color: #fff;
	text-align: left;
	padding-top: 25px;
	line-height: 28px;
}
/*手机*/
.screen-3__phone{
	width: 750px;
	height: 873px;
	background:url(../img/screen-3-phone.png) no-repeat center top;
	position: absolute;
	right: 0;
	top: 195px;
	z-index: 2;
}
/*左侧内容*/
.screen-3__features{
	position: absolute;
	top: 395px;
	left: 0;
	width: 320px;
	height: 280px;
}
.screen-3__features__item{
	width: 138px;
	height: 118px;
	border: 1px solid #cb7173;
	margin: 0 20px 20px 0;
	float: left;
	border-radius: 3px;
	color: #fff;
	text-align: center;
}
.screen-3__features__item__number{
	height: 36px;
	font-size: 36px;
	line-height: 36px;
	padding: 28px 0 8px;
}
.screen-3__features__item__desc{
	height: 14px;
	font-size: 14px;
	line-height: 14px;
}
/*第四屏*/
.screen-4{
	height: 800px;
	background-color: #fff;
	position: relative;
	overflow: hidden;
}
.screen-4__wrap{
	width: 1200px;
	height: auto;
	margin: 0 auto;
	position: relative;
}
/*大标题*/
.screen-4__heading{
	font-size: 46px;
	line-height: 46px;
	color: #f01400;
	text-align: center;
	padding-top: 135px;
}
/*子标题*/
.screen-4__subheading{
	font-size: 14px;
	color: #464a4f;
	text-align: center;
	padding-top: 29px;
	line-height: 28px;
}
/*手机型号*/
.screen-4__type{
	width: 1260px;
	height: 270px;
	position: absolute;
	top: 304px;
	margin-left: 30px;
}
/*单个手机*/
.screen-4__type__item{
	width: 220px;
	margin-right: 90px;
	height: 270px;
	float: left;
	position: relative;
	text-align: center;
	background-size: cover;
}
/*手机描述*/
.screen-4__type__item__color{
	width: 100%;
	height: 14px;
	line-height: 14px;
	font:14px;
	color: #2c3238;
	position: absolute;
	bottom: -44px;
}
.screen-4__type__item_i_1{
	background: url('../img/phone-1.png') no-repeat left top;
}
.screen-4__type__item_i_2{
	background: url('../img/phone-2.png') no-repeat left top;
}
.screen-4__type__item_i_3{
	background: url('../img/phone-3.png') no-repeat left top;
}
.screen-4__type__item_i_4{
	background: url('../img/phone-4.png') no-repeat left top;
}
.screen-4__type__item__storage{
	width: 100%;
	height: 12px;
	line-height: 12px;
	font:12px;
	color: #a4a9ae;
	position: absolute;
	bottom: -66px;
}
/*第五屏*/
.screen-5{
	height: 800px;
	position: relative;
	overflow: hidden;
	background-color: #d9dde1;
}
.screen-5__bg{
	width: 1920px;
	height: 433px;
	background:url(../img/bg-screen-5.png) no-repeat center;
	background-size: contain;
	position: absolute;
	left: 50%;
	margin-left: -960px;
	bottom: -100px;
}
/*大标题*/
.screen-5__heading{
	font-size: 46px;
	line-height: 46px;
	color: #f01400;
	text-align: center;
	padding-top: 130px;
}
/*子标题*/
.screen-5__subheading{
	font-size: 14px;
	color: #2c3137;
	text-align: center;
	padding-top: 25px;
	line-height: 28px;
}

/*第六屏*/
.screen-buy{
	height: 80px;
	padding: 120px 0;
	position: relative;
	overflow: hidden;
	background: #2b333b url('../img/bg-screen-buy.png') center no-repeat;
	text-align: center;
}
/*按钮*/
.screen-buy__button{
	height: 80px;
	width: 240px;
	text-align: center;
	line-height: 80px;
	font-size: 24px;
	color: #fff;
	background-color: #f01414;
	display: inline-block;
	border-radius: 3px;
	/*按钮的渐变效果*/
	transition: all .5s;
}
.screen-buy__button:hover{
	box-shadow: 0px 0px 10px #fff;
}
/*底部*/
.footer{
	height: 80px;
	line-height: 80px;
	text-align: center;
	color: #fff;
	font-size: 12px;
	background-color: #07111b;
}
/*导航侧边栏*/
.outline{
	position: fixed;
	padding: 5px 10px;
	bottom: 120px;
	right: 0;
	z-index: 3;
	background-color: #fff;
	box-shadow: 0 4px 12px rgba(0,0,0,.5)
}
.outline__item{
	display: block;
	width: 40px;
	height: 30px;
	line-height: 30px;
	text-align: center;
	padding: 5px 0;
	background-color: #fff;
	margin-top: 5px;
	border-top: 1px solid #eee;
	color: #93999f;
}
.outline__item:first-child{
	border: none;
}
.outline__item_status_active{
	color: red;
}


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2回答

同学你好,这边测试没有问题,一开始导航栏默认在顶部:

http://img1.sycdn.imooc.com//climg/5e59c0450932858d10590207.jpg

页面滚动的时候添加了类名,设置了固定定位:

http://img1.sycdn.imooc.com//climg/5e59c06809c32a0312170534.jpg

建议重新测试下,效果没有问题哦。

祝学习愉快!

好帮手慕星星 2020-02-28 19:31:44

同学你好,代码中也输出了滚动的值top为0,这是因为部分浏览器不兼容document.body.scrollTop 属性值,所以有问题。可以修改为:

http://img1.sycdn.imooc.com//climg/5e58fa0309c7c8f906990119.jpg

自己可以再测试下,祝学习愉快!

  • 提问者 Redamancy_Y6 #1
    老师,你太厉害了!我找了一天的错,原来是浏览器不兼容。想问一下老师,最上面的导航栏没有一直粘在顶部是什么问题?
    2020-02-28 19:44:01
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