日期:2014-05-17  浏览次数:20681 次

利用HTML5的classList API优化对样式名className的操作

HTML5的classList API提供了以下几个比较有用的控制CSS样式名的方法:

//添加一个class
elem.classList.add(classname);

//删除一个class
elem.classList.remove(classname);

//判断一个class是否已存在
elem.classList.contains(classname);

//如果class已存在则移除,如果不存在则添加
elem.classList.toggle(classname);
更多更详细的方法请参看HTML5 classList API。

这些方法以前是通过JavaScript来实现的,现在HTML5提供了这些原生的API,我们可以用它来优化以前用JavaScript来实现的操作方法,但是也要保证兼容不支持这几个API的浏览器。具体代码如下:

function N(id){return document.getElementById(id)}
N.trim = String.prototype.trim || function(str){
	return str.replace(/^\s+/, '').replace(/\s+$/, '');
};
if( document.createElement('p').classList ){
	N.addClass = function(elem, className){
		elem && elem.classList && elem.classList.add(className);
	};
	N.removeClass = function(elem, className){
		elem && elem.classList && elem.classList.remove(className);
	};
	N.hasClass = function(elem, className){
		return elem && elem.classList && elem.classList.contains(className);
	};
	N.toggleClass = function(elem, className){
		elem && elem.classList && elem.classList.toggle(className);
	};
	alert('Use html5 classList!');
}else{
	N.addClass = function(elem, className){
		if( elem ){
			var cn = elem.className;
			if(!cn){
				elem.className = className;
			}else if( (' '+cn+' ').indexOf(' '+className+' ')===-1 ){
				elem.className = className+' '+cn;
			}
		}
	};
	N.removeClass = function(elem, className){
		if( elem ){
			var cn = elem.className;
			elem.className = cn===className ? 
				'' : N.trim( (' '+cn+' ').replace(' '+className+' ', ' ') );
		}
	};
	N.hasClass = function(elem, className){
		if( elem && elem.className ){
			return (' '+elem.className+' ').indexOf(' '+className+' ') > -1;
		}
		return false;
	};
	N.toggleClass = function(elem, className){
		N.hasClass(elem, className) ? 
			N.removeClass(elem, className) : N.addClass(elem, className);
	};
}
HTML测试文件的源码如下,自己拿去测试去吧:

<!DOCTYPE html>
<html>
<head>
<title>利用HTML5的classList API优化样式名className操作</title>
<meta http-equiv="content-type" content="text/html;charset=utf-8">
<style type="text/css">
p{color:red;font-size:12px;}
.gree{color:#00ff00;}
.blue{color:#0000ff;}
.bold{font-weight:bold;}
.small{font-size:18px;}
.middle{font-size:32px;}
.big{font-size:56px;}
</style>
</head>
<body>

<p>默认字体和颜色是这样的。。。</p>   
<p id="p1">这是p1,原无class</p>
<p id="p2" class="gree bold">这是p2,原样式gree bold</p>
<p id="p3" class="gree bold">这是p3,原样式gree bold</p>
<p id="p4" class="gree bold">这是p4,原样式gree bold</p>
<p id="p5">这是p5,原无class</p>
<p id="p6" class="gree bold">这是p4,原样式gree bold</p>

<script type="text/javascript">
function N(id){return document.getElementById(id)}
N.trim = String.prototype.trim || function(str){
	return str.replace(/^\s+/, '').replace(/\s+$/, '');
};
if( document.createElement('p').classList ){
	N.addClass = function(elem, className){
		elem && elem.classList && elem.classList.add(className);
	};
	N.removeClass = function(elem, className){
		elem && elem.classList && elem.classList.remove(className);
	};
	N.hasClass = function(elem, className){
		return elem && elem.classList && elem.classList.contains(className);
	};
	N.toggleClass = function(elem, className){
		elem && elem.classList && elem.classList.toggle(className);
	};
	alert('Use html5 classList!');
}else{
	N.addClass = function(elem, className){
		if( elem ){
			var cn = elem.className;
			if(!cn){
				elem.className = className;
			}else if( (' '+cn+' ').indexOf(' '+className+' ')=