JS-DOM操作案例

2018-04-20 分类：JavaScript 作者：管理员阅读（692）

记录一次在妙味群里的作业，自己按要求做完后，老师很满意，但是老师提了个建议，DOM节点如果很多的时候，再去临时获取节点操作，对性能就不好了，不废话，两种解决方法，最终要告诉大家的一个道理：根据实际项目来选定那种方法来实现业务就行。

方法1:遍历节点循环添加事件

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>dom-操作</title>
</head>
<style>
body,ul,dl,dt,dd{
padding: 0;margin: 0;list-style: none;
}
#wrap{
width: 900px;
height: 400px;
background: linear-gradient(to right bottom,#21ffff,#ce6584);
position: absolute;
left: 0;
top: 0;
bottom: 0;
right: 0;
margin: auto;
box-sizing: border-box;
padding: 80px 0;
}
#content{
width: 700px;
height: 240px;
background: rgba(255,255,255,0.5);
margin: 0 auto;
}
#top-wrap{
height: 50px;
background: rgba(255,255,255,0.2);
}
.fl{
float: left;
}
.fr{
float: right;
}
.clearfix::after{
content: "";
display: block;
height: 0;
clear: both;
}
.top-l,.top-r{
float: left;
height: 100%;
font-size: 14px;
}
.top-l{
width: 100px;
line-height: 50px;
text-align: center;
}
.top-r{
width: calc(100% - 100px);
padding: 11px 0;
box-sizing: border-box;
}
.top-r li{
border: 2px solid #10aaff;
height: 24px;
line-height: 24px;
float: left;
padding: 0 5px;
margin-right: 5px;
display: none;
}
.details{
padding: 0 5px;
color: #10aaff;
}
.close{
padding: 0 5px;
color: #fff;
background: #10aaff;
cursor: pointer;
}
dl{
height: 40px;
line-height: 40px;
font-size: 14px;
}
dt{
padding-right:20px;
color: #848a8c;
}
dl dd{
float: left;
margin-right: 20px;
color: #181818;
cursor: pointer;
}
#inof-wrap{
padding: 15px 20px;
box-sizing: border-box;
background: rgba(255,255,255,0.6);
}
#inof-wrap dl:first-child{
border-bottom: 1px dashed #5acbd6;
}
#inof-wrap dl:nth-child(3){
border-bottom: 1px dashed #5acbd6;
border-top: 1px dashed #5acbd6;
}
.active{
color: #10aaff;
}
</style>
<body>
<div id="wrap">
<div id="content">
<div id="top-wrap">
<div class="top-l">你的选择:</div>
<ul class="top-r">
<li><span class="details">苹果</span><span class="close">×</span></li>
<li><span class="details">3.0英寸以下</span><span class="close">×</span></li>
<li><span class="details">安卓(Android)</span><span class="close">×</span></li>
<li><span class="details">联通3G</span><span class="close">×</span></li>
</ul>
</div>
<div id="inof-wrap">
<dl>
<dt class="fl">品牌:</dt>
<dd>苹果</dd>
<dd>小米</dd>
<dd>锤子</dd>
<dd>魅族</dd>
<dd>华为</dd>
<dd>OPPO</dd>
<dd>vivo</dd>
<dd>乐视</dd>
<dd>360</dd>
<dd>中兴</dd>
<dd>索尼</dd>
</dl>
<dl>
<dt class="fl">尺寸:</dt>
<dd>3.0英寸以下</dd>
<dd>3.0-3.9英寸</dd>
<dd>4.0-4.5英寸</dd>
<dd>4.6-4.9英寸</dd>
<dd>5.0-5.5英寸</dd>
<dd>6.0英寸以上</dd>
</dl>
<dl>
<dt class="fl">系统:</dt>
<dd>安卓(Android)</dd>
<dd>苹果(IOS)</dd>
<dd>微软(WindowsPhone)</dd>
<dd>无</dd>
<dd>其他</dd>
</dl>
<dl>
<dt class="fl">网络:</dt>
<dd>联通3G</dd>
<dd>双卡单4G</dd>
<dd>双卡双4G</dd>
<dd>联通4G</dd>
<dd>电信4G</dd>
<dd>移动4G</dd>
</dl>
</div>
</div>
</div>
</body>
<script>
"use strict";
let aLi=document.querySelectorAll('.top-r li');
let aClose=document.querySelectorAll('.top-r .close');
let aDl=document.querySelectorAll('#inof-wrap dl');
let aDd=document.querySelectorAll('#inof-wrap dl dd');
for(let i=0;i<aDd.length;i++){
aDd[i].onclick=function(){
//父元素 dl的index索引值
let parent_index=this.parentNode.index;
//点击的dd里的内容
let dd_content=this.innerText;
//如果点击的dd没有active的类并且active类没有在当前dl里的dd的dom身上
if(this.getAttribute("class")!=="active" && !this.parentNode.querySelector('.active')){
//点击的dd就给加个active类
this.className="active";
}else{//如果已经存在类了，点击的dd添加上active类，当前dl里的dd已经存在的去掉active类
this.parentNode.querySelector('.active').className="";
this.className="active";
}
//对应索引值的li的内容和显示隐藏控制
aLi[parent_index].style.display="block";
aLi[parent_index].querySelector('.details').innerHTML=dd_content;
}
}
for(let i=0;i<aClose.length;i++){
//给关闭按钮和dl添加自定义索引值
aClose[i].index=i;
aDl[i].index=i;
//关闭按钮注册点击事件
aClose[i].onclick=function(){
this.parentNode.querySelector('.details').innerHTML='';
this.parentNode.style.display='none';
aDl[this.index].querySelector('.active').className="";
}
}
</script>
</html>

考虑性能的话，这个方法的缺点是：在点击事件中临时获取dom元素对性能不太友好，所以我又用事件委托写了第二种方法。如下

事件委托

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>dom-操作-2</title>
</head>
<style>
body,ul,dl,dt,dd{
padding: 0;margin: 0;list-style: none;
}
#wrap{
width: 900px;
height: 400px;
background: linear-gradient(to right bottom,#21ffff,#ce6584);
position: absolute;
left: 0;
top: 0;
bottom: 0;
right: 0;
margin: auto;
box-sizing: border-box;
padding: 80px 0;
}
#content{
width: 700px;
height: 240px;
background: rgba(255,255,255,0.5);
margin: 0 auto;
}
#top-wrap{
height: 50px;
background: rgba(255,255,255,0.2);
}
.fl{
float: left;
}
.fr{
float: right;
}
.clearfix::after{
content: "";
display: block;
height: 0;
clear: both;
}
.top-l,.top-r{
float: left;
height: 100%;
font-size: 14px;
}
.top-l{
width: 100px;
line-height: 50px;
text-align: center;
}
.top-r{
width: calc(100% - 100px);
padding: 11px 0;
box-sizing: border-box;
}
.top-r li{
border: 2px solid #10aaff;
height: 24px;
line-height: 24px;
float: left;
padding: 0 5px;
margin-right: 5px;
display: none;
}
.details{
padding: 0 5px;
color: #10aaff;
}
.close{
padding: 0 5px;
color: #fff;
background: #10aaff;
cursor: pointer;
}
dl{
height: 40px;
line-height: 40px;
font-size: 14px;
}
dt{
padding-right:20px;
color: #848a8c;
}
dl dd{
float: left;
margin-right: 20px;
color: #181818;
cursor: pointer;
}
#inof-wrap{
padding: 15px 20px;
box-sizing: border-box;
background: rgba(255,255,255,0.6);
}
#inof-wrap dl:first-child{
border-bottom: 1px dashed #5acbd6;
}
#inof-wrap dl:nth-child(3){
border-bottom: 1px dashed #5acbd6;
border-top: 1px dashed #5acbd6;
}
.active{
color: #10aaff;
}
</style>
<body>
<div id="wrap">
<div id="content">
<div id="top-wrap">
<div class="top-l">你的选择:</div>
<ul class="top-r">
<li><span class="details">苹果</span><span class="close">×</span></li>
<li><span class="details">3.0英寸以下</span><span class="close">×</span></li>
<li><span class="details">安卓(Android)</span><span class="close">×</span></li>
<li><span class="details">联通3G</span><span class="close">×</span></li>
</ul>
</div>
<div id="inof-wrap">
<dl>
<dt class="fl">品牌:</dt>
<dd>苹果</dd>
<dd>小米</dd>
<dd>锤子</dd>
<dd>魅族</dd>
<dd>华为</dd>
<dd>OPPO</dd>
<dd>vivo</dd>
<dd>乐视</dd>
<dd>360</dd>
<dd>中兴</dd>
<dd>索尼</dd>
</dl>
<dl>
<dt class="fl">尺寸:</dt>
<dd>3.0英寸以下</dd>
<dd>3.0-3.9英寸</dd>
<dd>4.0-4.5英寸</dd>
<dd>4.6-4.9英寸</dd>
<dd>5.0-5.5英寸</dd>
<dd>6.0英寸以上</dd>
</dl>
<dl>
<dt class="fl">系统:</dt>
<dd>安卓(Android)</dd>
<dd>苹果(IOS)</dd>
<dd>微软(WindowsPhone)</dd>
<dd>无</dd>
<dd>其他</dd>
</dl>
<dl>
<dt class="fl">网络:</dt>
<dd>联通3G</dd>
<dd>双卡单4G</dd>
<dd>双卡双4G</dd>
<dd>联通4G</dd>
<dd>电信4G</dd>
<dd>移动4G</dd>
</dl>
</div>
</div>
</div>
</body>
<script>
"use strict";
let oWrap=document.querySelector('#inof-wrap');
let oUl=document.querySelector('.top-r');
let aLi=document.querySelectorAll('.top-r li');
let aClose=document.querySelectorAll('.top-r .close');
let aDl=document.querySelectorAll('#inof-wrap dl');
let aDd=document.querySelectorAll('#inof-wrap dl dd');
oWrap.addEventListener('click',function(ev){
//事件对象兼容写法
let e=ev||window.event;

//点击的目标元素
let _clickEle=e.target;

//点击的元素是dd
if( _clickEle.tagName === 'DD' ){

//点击的对应的父元素dl的索引值
let _index=_clickEle.parentNode.index;
//对应索引值的dl下面的dd没有active类
if(!aDl[_index].querySelector('.active')){

//点击的dd加上active类
_clickEle.className='active';

}else{//如果已经存在active类先移除再给点击的dd添加active类

//先移除active类
aDl[_index].querySelector('.active').className='';

//点击的dd再加上active类
_clickEle.className='active';
}

//选择对应的li显示和内容对应改变
aLi[_index].style.display='block';
aLi[_index].querySelector('.details').innerHTML=_clickEle.innerHTML;
}
},false);

//关闭按钮操作
oUl.addEventListener('click',function(ev){
//事件对象兼容写法
let e=ev||window.event;
//点击的元素是关闭按钮
if( e.target.className === 'close' ){
//li的索引值
let _index=e.target.parentNode.index;
//点击关闭按钮对应索引值的li隐藏
aLi[_index].style.display='none';
//点击关闭按钮对应索引值下面的dl下面的有active类的自己移除掉active
aDl[_index].querySelector('.active').className='';
}
},false);

//自定义索引值属性
for(let i=0; i<aLi.length; i++){
aLi[i].index=i;
aDl[i].index=i;
}
</script>
</html>

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