老师我试着自己重新编了一下js，有一点问题

老师我试着自己重新编了一下js，有一点问题

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Document</title>
<link rel="stylesheet" type="text/css" href="jstext.css">
<link rel="stylesheet" type="text/css" href="animate.css">
</head>
<body>
<!-- 头部部分 -->
<header class='header'>
<div class='header__logo header__logo_animate_init'>H5实战页面</div>
<div class='header__nav header__nav_animate_init'>
<a href="javescript:;" class='header__nav-item'>实战课程</a>
<a href="javescript:;" class='header__nav-item'>商业案例</a>
<a href="javescript:;" class='header__nav-item'>课程体系</a>
<a href="javescript:;" class='header__nav-item'>集成环境</a>
<a href="javescript:;" class='header__nav-item'>云端学习</a>
<a href="javescript:;" class='header__nav-item header__nav-item-button'>即刻学习</a>
<div class='header__nav__line'></div>
</div>
</header>
<!-- 第一屏 -->
<div class='screen-1'>
<div class='screen-1__heading screen-1__heading_animate_init'>实战课重磅上线</div>
<div class='screen-1__subheading screen-1__subheading_animate_init'>一键云学习，还在等待什么</div>
</div>
<!-- 第二屏 -->
<div class='screen-2'>
<div class='screen-2__heading'>每门课都是真实商业案例</div>
<div class='screen-2__line'></div>
<div class='screen-2__subheading'>真实案例，真实场景，在实站中实践、操作、调试<br>
大牛带你体验BAT真实开发流程，所有开发过程为你一一呈现。
</div>
<div class='screen-2__picture-1'></div>
<div class='screen-2__picture-2'></div>
<div class='screen-2__picture-3'></div>
</div>
<!-- 第三屏 -->
<div class='screen-3'>
<div class='screen-3__wrap'>
<div class='screen-3__heading'>强大的语言课程体系支持</div>
<div class='screen-3__line'></div>
<div class='screen-3__subheading'>学习环境与课程轻松对接，安调、调试、写入、部署、运行，一站式解决<br>，让你体验开发全流程</div>
<div class='screen-3__lang'>
<div class='screen-3__lang-item screen-3__lang-item-1'>HTMLS</div>
<div class='screen-3__lang-item screen-3__lang-item-2'>PHP</div>
<div class='screen-3__lang-item screen-3__lang-item-3'>JAVA</div>
<div class='screen-3__lang-item screen-3__lang-item-4'>Python</div>
<div class='screen-3__lang-item screen-3__lang-item-5'>Node.js</div>
</div>
</div>
</div>
<!-- 第四屏 -->
<div class='screen-4'>
<div class='screen-4__heading'>省去本地复杂的环境搭建</div>
<div class='screen-4__line'></div>
<div class='screen-4__subheading'>你可以告别在虚拟机中调试开发了</div>
<div class='screen-4__wrap'>
<div class='screen-4__wrap__item screen-4__wrap__item-1'>
<div class='screen-4__wrap__item-text'>实战课程集成开发环境</div>
</div>
<div class='screen-4__wrap__item screen-4__wrap__item-2'>
<div class='screen-4__wrap__item-text'>内置终端命令行</div>
</div>
<div class='screen-4__wrap__item screen-4__wrap__item-3'>
<div class='screen-4__wrap__item-text'>编译你的应用程序</div>
</div>
<div class='screen-4__wrap__item screen-4__wrap__item-4'>
<div class='screen-4__wrap__item-text'>通过云端服务输出效果</div>
</div>
</div>
</div>
<!-- 第五屏 -->
<div class='screen-5'>
<div class='screen-5__heading'>云端学习可以这样简单</div>
<div class='screen-5__line'></div>
<div class='screen-5__subheading'>看视频，敲代码一气呵成。结合慕课网为你提供的云端学习工具，所见即所得，从此学习不一样。</div>
<div class='screen-5__picture'></div>
</div>
<!-- 第六屏 -->
<div class='screen-6'>
<a href="javescript:;" class='screen-6__a'>继续了解学习体验</a>
</div>
<footer class='footer'>
<div class='footer__wrap'>
<div class='footer__wrap-top'>
<a href="javascript:;">网站首页</a>
<a href="javascript:;">人才招聘</a>
<a href="javascript:;">联系我们</a>
<a href="javascript:;">高校联盟</a>
<a href="javascript:;">关于我们</a>
<a href="javascript:;">讲师招募</a>
<a href="javascript:;">意见反馈</a>
<a href="javascript:;">友情链接</a>
</div>
<div class='footer__wrap-bottom'>Copyright © 2015 imooc.com All Rights Reserved | 京ICP备 13046642号-2</div>
</div>
</footer>
<div class='sidenav'>
<a href="javascript:;" class='sidenav__item'>字</a>
<a href="javascript:;" class='sidenav__item'>看</a>
<a href="javascript:;" class='sidenav__item'>不</a>
<a href="javascript:;" class='sidenav__item'>清</a>
<a href="javascript:;" class='sidenav__item'>呐</a>
</div>
<script type="text/javascript" src='jstext.js'></script>
</body>
</html>


css

*{
	margin:0;
	padding:0;
	border:none;
}
body{
	font-family: '微软雅黑';
}
a{
	text-decoration: none;
}
/*头部部分*/
.header{
	width:100%;
	height:60px;
	background:rgba(0,0,0,0);
	position: relative;
	float:left;
	z-index:3;
}
.header_status_black{
	background:rgba(255,255,255,.5);
	position: fixed;
	top: 0;
}
.header_status_black .header__logo,
.header_status_black .header__nav-item{
	color:#444;
}
.header_status_black .header__nav-item-button{
	color:#fff;
}
.header__logo{
	width:200px;
	height:60px;
	line-height: 60px;
	font-size: 20px;
	color:#fff;
	padding-left:50px;
	background:url(图片素材/img/logo.png) left center no-repeat;
	background-size: 40px 40px;
	position: absolute;
	top:0;
	left:10px;
}
.header__nav{
	height:40px;
	position: absolute;
	right:30px;
	top: 50%;
	margin-top:-20px;
	float:right;
}
.header__nav-item{
	width:48px;
    height: 40px;
    line-height: 40px;
	font-size:12px;
	color:#fff;
	padding-left:40px;
	display: block;
	float:left;
}
.header__nav-item-button{
	width:96px;
	height:40px;
	background-color: #f00;
	border-radius: 3px;
	margin-left:40px;
}
.header__nav__line{
	width:48px;
	height:2px;
	position:absolute;
	bottom:0;
	left:40px;
	background:red;
	transition: all .5s;
}
.header_status_black .header__nav-item_status_active{
	color:#000;
	font-weight: bold;
}
/*第一屏*/
.screen-1{
	height:637px;
	background: url(图片素材/img/sc1.jpg) center no-repeat;
	background-size:cover;
}
.screen-1__heading{
	font-size:40px;
	text-align: center;
	padding-top: 240px;
	color:#fff;
}
.screen-1__subheading{
	font-size: 15px;
	text-align: center;
	padding-top:33px;
	color:#fff;
}

/*第二屏*/
.screen-2{
	height:640px;
	background-color: #f3f5f7;
	position: relative;
}
.screen-2__heading{
	font-size:40px;
	font-weight: bold;
	text-align: center;
	padding-top: 90px;
	color:#07111b;
}
.screen-2__line{
	width:50px;
	height:3px;
	background-color: #f00;
	position: absolute;
	top:168px;
	left:50%;
	margin-left: -25px;
}
.screen-2__subheading{
	height:20px;
	line-height: 20px
	font-size: 15px;
	text-align: center;
	padding-top:60px;
	color:#07111b;
}
.screen-2__picture-1{
	width:750px;
	height:361px;
	background:url(图片素材/img/sc2.png);
	position: absolute;
	left:50%;
	bottom:0;
	margin-left:-375px;
}
.screen-2__picture-2{
	width:275px;
	height:380px;
	background:url(图片素材/img/sc2-1.png);
	position: absolute;
	left:50%;
	bottom:0;
	margin-left:-128.5px;
	z-index:3;
}
.screen-2__picture-3{
	width:266px;
	height:205px;
	background:url(图片素材/img/sc2-2.png);
	position: absolute;
	left:50%;
	bottom:100px;
	margin-left:-30px;
}

/*第三屏*/
.screen-3{
	background:url(图片素材/img/sc3.png) #2b333b 130px center no-repeat;
	background-size: 570px 620px;
	height:640px;
}
.screen-3__wrap{
	width:1200px;
	height:640px;
	margin:0 auto;
	position:relative;
}
.screen-3__heading{
	font-size:40px;
	padding: 214px 0 0 670px;
	color:#fff;
}
.screen-3__line{
	width:50px;
	height:3px;
	background-color: #f00;
	position: absolute;
	top:295px;
	left:670px;
}
.screen-3__subheading{
	font-size: 15px;
	padding: 59px 0 0 670px;
	color:#fff;
}
.screen-3__lang{
	height:70px;
	position: absolute;
	bottom:48px;
	left:670px;
}
.screen-3__lang-item{
	width:60px;
	font-size:10px; 
	height:60px;
    line-height: 60px;
    text-align: center;
	border-radius: 50%;
	float:left;
	margin-right: 36px;
}
.screen-3__lang-item-1{
	border:3px solid #1f5975;
	color:#17b0ff;
}
.screen-3__lang-item-2{
	border:3px solid #424d76;
	color:#7888fd;
}
.screen-3__lang-item-3{
	border:3px solid #6b4146;
	color:#ff584c;
}
.screen-3__lang-item-4{
	border:3px solid #29535f;
	color:#24c7ca;
}
.screen-3__lang-item-5{
	border:3px solid #3e4e40;
	color:#90bd56;
}


/*第四屏*/
.screen-4{
	height:640px;
	background-color: #f3f5f7;
	position: relative;
}
.screen-4__heading{
	font-size:40px;
	font-weight: bold;
	text-align: center;
	padding-top: 90px;
	color:#07111b;
}
.screen-4__line{
	width:50px;
	height:3px;
	background-color: #f00;
	position: absolute;
	top:168px;
	left:50%;
	margin-left: -25px;
}
.screen-4__subheading{
	height:20px;
	line-height: 20px
	font-size: 15px;
	text-align: center;
	padding-top:60px;
	color:#07111b;
}
/*第四屏下方四个图片*/
.screen-4__wrap{
	width:1110px;
	height:120px;
	position: absolute;
	top:290px;
	left:50%;
	margin-left:-540px;
}
.screen-4__wrap__item{
	float:left;
}
.screen-4__wrap__item-text{
	width: 180px;
	color: #07111b;
	position: absolute;
	bottom:0;
	text-align: center;
}
.screen-4__wrap__item-1{
	width:180px;
	height:120px;
	margin-right:130px;
	background:url(图片素材/img/sc4-1.png) center top no-repeat;
}
.screen-4__wrap__item-2{
	width:180px;
	height:120px;
	margin-right:130px;
	background:url(图片素材/img/sc4-2.png) center top no-repeat;
}
.screen-4__wrap__item-3{
	width:180px;
	height:120px;
	margin-right:130px;
	background:url(图片素材/img/sc4-3.png) center top no-repeat;
}
.screen-4__wrap__item-4{
	width:180px;
	height:120px;
	background:url(图片素材/img/sc4-4.png) center top no-repeat;
}

/*第五屏*/
.screen-5{
	height:640px;
	background:url(图片素材/img/sc5.jpg) center no-repeat;
	background-size: cover; 
	position: relative;
}
.screen-5__heading{
	font-size:40px;
	font-weight: bold;
	text-align: center;
	padding-top: 334px;
	color:#fff;
}
.screen-5__line{
	width:50px;
	height:3px;
	background-color: #fff;
	position: absolute;
	top:412px;
	left:50%;
	margin-left: -25px;
}
.screen-5__subheading{
	height:20px;
	line-height: 20px
	font-size: 15px;
	text-align: center;
	padding-top:60px;
	color:#fff;
}
.screen-5__picture{
	width:200px;
	height:200px;
	background:url(图片素材/img/sc5-1.png);
	position: absolute;
	left:50%;
	top:100px;
	margin-left:-100px;
}

/*第六屏*/
.screen-6{
	height:200px;
	background-color: #fff;
	position: relative;
}
.screen-6__a{
	color:#14191e;
	width:240px;
	height:60px;
	line-height: 60px;
	text-align: center;
	border:1px solid #707070;
	border-radius: 3px;
	display: block;
	position: absolute;
	top:50%;
	left:50%;
	margin-top: -30px;
	margin-left: -120px;
}
.screen-6__a:hover{
	color:red;
}
/*尾部*/
.footer{
	height:105px;
	background:#000;
	text-indent: center;
	position: relative;
}
.footer__wrap{
	width:660px;
	height:45px;
	position: absolute;
	top:50%;
	left:50%;
	margin-top:-22.5px;
	margin-left: -330px;
}
.footer__wrap-top{
	height:30px;
}
.footer__wrap-top>a{
	margin-right: 30px;
	display: inline-block;
	height:20px;
	line-height: 20px;
	font-size:11px;
	color:#bbc096;
}
.footer__wrap-bottom{
	height:30px;
	line-height: 30px
	font-size:16px;
	color:#527d82;
	text-align: center;
}
/*侧边导航栏*/
.sidenav{
	position: fixed;
	right: 0;
	bottom: 200px;
	padding:10px;
	z-index:3;
	background:#fff;
	box-shadow: 0 0 5px rgba(0,0,0,.5);
}
.sidenav__item{
	width:20px;
	height:25px;
	line-height: 25px;
	text-align: center;
	display: block;
	color:#000;
	margin-bottom: 5px;
}
.sidenav__item_active{
	color:red;
}


动画css

/*头部动画*/
.header__logo,
.header__nav,
.header_status_black{
	transition: all 1s;
}

.header__logo_animate_init,
.header__nav_animate_init{
	transform:translate(0,-100%);
	opacity:0;
}
.header__logo_animate_done,
.header__nav_animate_done{
	transform:translate(0,0);
	opacity:1;
}

/*screen-1动画*/
.screen-1__heading{
	transition: all 1s;
}
.screen-1__subheading{
	transition: all 1s .5s;
}
.screen-1__heading_animate_init,
.screen-1__subheading_animate_init{
	transform:translate(0,100%);
	opacity:0;
}
.screen-1__heading_animate_done,
.screen-1__subheading_animate_done{
	transform:translate(0,0);
	opacity:1;
}

/*第二屏动画*/
.screen-2__heading{
	transition: all 1s;
}
.screen-2__line,
.screen-2__subheading,
.screen-2__picture-2{
	transition:all 1s .2s;
}
.screen-2__picture-3{
	transition:all 1s 1s;
}


.screen-2__heading_animate_init,
.screen-2__subheading_animate_init{
	transform:translate(0,100%);
	opacity:0;
}
.screen-2__heading_animate_done,
.screen-2__subheading_animate_done{
	transform:translate(0,0);
	opacity:1;
}
.screen-2__line_animate_init,
.screen-2__picture-2_animate_init{
	opacity:0;
}
.screen-2__line_animate_done,
.screen-2__picture-2_animate_done{
	opacity:1;
}
.screen-2__picture-3_animate_init{
	transform: translate(0,100%);
	opacity:0;
}
.screen-2__picture-3_animate_done{
	-webkit-animation:tb 1s 1s;
}
@-webkit-keyframes tb{
	0%{transform: translate(0,100%);}
	60%{transform: translate(0,0);}
	90%{transform: translate(0,5%);}
	100%{transform: translate(0,0%);}
}
/*第三屏*/
.screen-3__heading{
	transition: all 1s;
}
.screen-3__line,
.screen-3__subheading{
	transition: all 1s .5s;
}
.screen-3__lang{
	transition: all 1s 1s;
}
.screen-3__heading_animate_init,
.screen-3__subheading_animate_init{
	transform:translate(0,100%);
	opacity:0;
}
.screen-3__heading_animate_done,
.screen-3__subheading_animate_done{
	transform:translate(0,0);
	opacity:1;
}
.screen-3__line_animate_init{
	opacity:0;
}
.screen-3__line_animate_done{
	opacity:1;
}
.screen-3__lang_animate_init{
	transform: translate(0,100%);
	opacity:0;
}
.screen-3__lang_animate_done{
	-webkit-animation:tb 1s 1s;
}
/*.screen-3__lang-item-1_animate_init,
.screen-3__lang-item-2_animate_init,
.screen-3__lang-item-3_animate_init,
.screen-3__lang-item-4_animate_init,
.screen-3__lang-item-5_animate_init{
	transform: translate(0,100%);
	opacity:0;
}
.screen-3__lang-item-1_animate_done,
.screen-3__lang-item-2_animate_done,
.screen-3__lang-item-3_animate_done,
.screen-3__lang-item-4_animate_done,
.screen-3__lang-item-5_animate_done{
	-webkit-animation:tb 1s 1s;
}*/

/*第四屏*/
.screen-4__heading,
.screen-4__wrap__item-1,
.screen-4__wrap__item-2,
.screen-4__wrap__item-3,
.screen-4__wrap__item-4{
	transition: all 1s;
}
.screen-4__line,
.screen-4__subheading{
	transition: all 1s .5s;
}
.screen-4__heading_animate_init,
.screen-4__subheading_animate_init{
	transform:translate(0,100%);
	opacity:0;
}
.screen-4__heading_animate_done,
.screen-4__subheading_animate_done{
	transform:translate(0,0);
	opacity:1;
}
.screen-4__line_animate_init{
	opacity: 0;
}
.screen-4__line_animate_done{
	opacity: 1;
}
.screen-4__wrap__item-1_animate_init,
.screen-4__wrap__item-2_animate_init,
.screen-4__wrap__item-3_animate_init,
.screen-4__wrap__item-4_animate_init{
	transform: scale(0);
	opacity:0;
}
.screen-4__wrap__item-1_animate_done,
.screen-4__wrap__item-2_animate_done,
.screen-4__wrap__item-3_animate_done,
.screen-4__wrap__item-4_animate_done{
	transform: scale(1);
	opacity:1;
}
/*第五屏*/
.screen-5__heading,
.screen-5__picture{
	transition: all 1s;
}
.screen-5__line,
.screen-5__subheading{
	transition: all 1s .5s;
}
.screen-5__picture_animate_init{
	transform: scale(0);
	opacity:0;
}
.screen-5__picture_animate_done{
	transform: scale(1);
	opacity:1;
}
.screen-5__heading_animate_init,
.screen-5__subheading_animate_init{
	transform:translate(0,100%);
	opacity:0;
}
.screen-5__heading_animate_done,
.screen-5__subheading_animate_done{
	transform:translate(0,0);
	opacity:1;
}
.screen-5__line_animate_init{
	opacity: 0;
}
.screen-5__line_animate_done{
	opacity: 1;
}

/*侧边导航栏*/
.sidenav{
	transition:all 1s;
	transform: translate(100%,0);
	opacity:0;
}
.sidenav_animate_done{
	transform: translate(0,0);
	opacity:1;
}


js


var getEle=function(idx){
	return document.querySelector(idx);
}
var getEles=function(idx){
	return document.querySelectorAll(idx);
}
var getClass=function(element){
	return element.getAttribute('class');
}
var setClass=function(element,newclass){
    return element.setAttribute('class',newclass)
}
var addClass=function(element,newclass){
	var base=getClass(element);
	return setClass(element,base+' '+newclass);
}
var screenAnimateElements={
	'.header':[
		'.header__logo',
		'.header__nav'
	],
	'.screen-1':[
		'.screen-1__heading',
		'.screen-1__subheading'
	],
	'.screen-2':[
		'.screen-2__heading',
		'.screen-2__line',
		'.screen-2__subheading',
		'.screen-2__picture-2',
		'.screen-2__picture-3'
	],
	'.screen-3':[
		'.screen-3__wrap',
		'.screen-3__heading',
		'.screen-3__line',
		'.screen-3__lang',
		'.screen-3__subheading',
		'.screen-3__lang-item-1',
		'.screen-3__lang-item-2',
		'.screen-3__lang-item-3',
		'.screen-3__lang-item-4',
		'.screen-3__lang-item-5'
	],
	'.screen-4':[
		'.screen-4__heading',
		'.screen-4__line',
		'.screen-4__subheading',
		'.screen-4__wrap__item-1',
		'.screen-4__wrap__item-2',
		'.screen-4__wrap__item-3',
		'.screen-4__wrap__item-4'
	],
	'.screen-5':[
		'.screen-5__heading',
		'.screen-5__line',
		'.screen-5__subheading',
		'.screen-5__picture'
	]
};

// 使所有元素初始化函数
var screenAnimateInit=function(selector){                                       
	var screen=getEle(selector);
	var animateScreen=screenAnimateElements[selector];
	for(var i=0;i<animateScreen.length;i++){
		var elements=getEle(animateScreen[i]);
		addClass(elements,animateScreen[i].substr(1)+'_animate_init')   
	}
}

window.onload=function(){
	for(k in screenAnimateElements){
	    screenAnimateInit(k);
	    if(k==='.screen-1'){
	    	continue;
    	}
    }
}

// 播放动画函数
var screenAnimatedone=function(selector){                                       
	var screen=getEle(selector);
	var animateScreen=screenAnimateElements[selector];
	for(var i=0;i<animateScreen.length;i++){
		var elements=getEle(animateScreen[i]);
		console.log(elements);
		var baseCls=getClass(elements);
        console.log(baseCls);
		elements.setAttribute('class',baseCls.replace('_animate_init','_animate_done')); 
	}
}
screenAnimatedone('.screen-1');
// 根据滚动条来播放动画的函数
// window.onscroll=function(){
// 	var top=document.documentElement.scrollTop;
// 	console.log(top);
// 	if(top>-1){
//   	switchNavItemsActive(0);
//   }
  
//   if(top>300){
//   	playScreenAnimateDone('.screen-2');
//   	switchNavItemsActive(1);
//   } 
//   if(top>900){
//   	playScreenAnimateDone('.screen-3');
//   	switchNavItemsActive(2);
//   } 
//   if(top>1500){
//   	playScreenAnimateDone('.screen-4');
//   	switchNavItemsActive(3);
//   } 
//   if(top>2100){
//   	playScreenAnimateDone('.screen-5');
//   	switchNavItemsActive(4);
//   }
// }

老师为什么我的播放动画的函数只能获取到一开始的class属性值，而获取不到之后我新加给他的值。

就像这样

http://img1.sycdn.imooc.com//climg/5ca5bc65000164c413670583.jpg
CC陈十一 2019-04-04
源自：宣传页项目   5-6 作业题
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1回答
好帮手慕慕子 回答被采纳获得+3积分 2019-04-04 18:26:13

同学你好， 这是因为使用querySelector获取的是静态集合，选取出元素之后就和文档的改变无关了。

建议： 可以参考getElementById()或者getElementsByClassName()方法获取元素， 这个方法获取的集合是动态的，获取的元素会随着文档改变

如果帮帮助到了你 欢迎采纳

祝学习愉快~~~

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  • CC陈十一 提问者 #1
    好的，谢谢老师
    2019-04-04 18:32:09
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