前端基础——兼容性
一、CSS兼容性问题
1、HTML5 标签的兼容
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8"/>
<title></title>
<!--如果有很多HTML5的标签，那样就会创建出太多的自定义元素了，所以下面可以用一个JS库去兼容-->
<script src="js/html5shiv.js"></script>
<!--<script type="text/javascript">
// 用JS创建一个自定义元素,自定义元素为内联元素,需要在样式中转化为块元素
document.createElement("header");
document.createElement("section");
document.createElement("footer");
</script>-->
<style type="text/css">
header{
width: 200px;
height: 200px;
display: block; /*设置行内块元素与JS获得IE6的兼容*/
background: #000000;
}
section{
width: 150px;
height: 150px;
display: block; /*设置行内块元素与JS获得IE6的兼容*/
background: #eee999;
}
footer{
width: 100px;
height: 100px;
display: block; /*设置行内块元素与JS获得IE6的兼容*/
background: #999999;
}
</style>
</head>
<body>
<header>header</header>
<section>section</section>
<footer>footer</footer>
</body>
</html>
html5shiv.js 兼容库代码，如下：
/*! HTML5 Shiv v3.6.1 | @afarkas @jdalton @jon_neal @rem | MIT/GPL2 Licensed */
(function(window, document) {
/*jshint evil:true */
/** Preset options */
var options = window.html5 || {};
/** Used to skip problem elements */
var reSkip = /^<|^(?:button|map|select|textarea|object|iframe|option|optgroup)$/i;
/** Not all elements can be cloned in IE **/
var saveClones = /^(?:a|b|code|div|fieldset|h1|h2|h3|h4|h5|h6|i|label|li|ol|p|q|span|strong|style|table|tbody|td|th|tr|ul)$/i;
/** Detect whether the browser supports default html5 styles */
var supportsHtml5Styles;
/** Name of the expando, to work with multiple documents or to re-shiv one document */
var expando = '_html5shiv';
/** The id for the the documents expando */
var expanID = 0;
/** Cached data for each document */
var expandoData = {};
/** Detect whether the browser supports unknown elements */
var supportsUnknownElements;
(function() {
try {
var a = document.createElement('a');
a.innerHTML = '<xyz></xyz>';
//if the hidden property is implemented we can assume, that the browser supports basic HTML5 Styles
supportsHtml5Styles = ('hidden' in a);
supportsUnknownElements = a.childNodes.length == 1 || (function() {
// assign a false positive if unable to shiv
(document.createElement)('a');
var frag = document.createDocumentFragment();
return (
typeof frag.cloneNode == 'undefined' ||
typeof frag.createDocumentFragment == 'undefined' ||
typeof frag.createElement == 'undefined'
);
}());
} catch(e) {
supportsHtml5Styles = true;
supportsUnknownElements = true;
}
}());
/*--------------------------------------------------------------------------*/
/**
* Creates a style sheet with the given CSS text and adds it to the document.
* @private
* @param {Document} ownerDocument The document.
* @param {String} cssText The CSS text.
* @returns {StyleSheet} The style element.
*/
function addStyleSheet(ownerDocument, cssText) {
var p = ownerDocument.createElement('p'),
parent = ownerDocument.getElementsByTagName('head')[0] || ownerDocument.documentElement;
p.innerHTML = 'x<style>' + cssText + '</style>';
return parent.insertBefore(p.lastChild, parent.firstChild);
}
/**
* Returns the value of `html5.elements` as an array.
* @private
* @returns {Array} An array of shived element node names.
*/
function getElements() {
var elements = html5.elements;
return typeof elements == 'string' ? elements.split(' ') : elements;
}
/**
* Returns the data associated to the given document
* @private
* @param {Document} ownerDocument The document.
* @returns {Object} An object of data.
*/
function getExpandoData(ownerDocument) {
var data = expandoData[ownerDocument[expando]];
if (!data) {
data = {};
expanID++;
ownerDocument[expando] = expanID;
expandoData[expanID] = data;
}
return data;
}
/**
* returns a shived element for the given nodeName and document
* @memberOf html5
* @param {String} nodeName name of the element
* @param {Document} ownerDocument The context document.
* @returns {Object} The shived element.
*/
function createElement(nodeName, ownerDocument, data){
if (!ownerDocument) {
ownerDocument = document;
}
if(supportsUnknownElements){
return ownerDocument.createElement(nodeName);
}
if (!data) {
data = getExpandoData(ownerDocument);
}
var node;
if (data.cache[nodeName]) {
node = data.cache[nodeName].cloneNode();
} else if (saveClones.test(nodeName)) {
node = (data.cache[nodeName] = data.createElem(nodeName)).cloneNode();
} else {
node = data.createElem(nodeName);
}
// Avoid adding some elements to fragments in IE < 9 because
// * Attributes like `name` or `type` cannot be set/changed once an element
// is inserted into a document/fragment
// * Link elements with `src` attributes that are inaccessible, as with
// a 403 response, will cause the tab/window to crash
// * Script elements appended to fragments will execute when their `src`
// or `text` property is set
return node.canHaveChildren && !reSkip.test(nodeName) ? data.frag.appendChild(node) : node;
}
/**
* returns a shived DocumentFragment for the given document
* @memberOf html5
* @param {Document} ownerDocument The context document.
* @returns {Object} The shived DocumentFragment.
*/
function createDocumentFragment(ownerDocument, data){
if (!ownerDocument) {
ownerDocument = document;
}
if(supportsUnknownElements){
return ownerDocument.createDocumentFragment();
}
data = data || getExpandoData(ownerDocument);
var clone = data.frag.cloneNode(),
i = 0,
elems = getElements(),
l = elems.length;
for(;i<l;i++){
clone.createElement(elems[i]);
}
return clone;
}
/**
* Shivs the `createElement` and `createDocumentFragment` methods of the document.
* @private
* @param {Document|DocumentFragment} ownerDocument The document.
* @param {Object} data of the document.
*/
function shivMethods(ownerDocument, data) {
if (!data.cache) {
data.cache = {};
data.createElem = ownerDocument.createElement;
data.createFrag = ownerDocument.createDocumentFragment;
data.frag = data.createFrag();
}
ownerDocument.createElement = function(nodeName) {
//abort shiv
if (!html5.shivMethods) {
return data.createElem(nodeName);
}
return createElement(nodeName, ownerDocument, data);
};
ownerDocument.createDocumentFragment = Function('h,f', 'return function(){' +
'var n=f.cloneNode(),c=n.createElement;' +
'h.shivMethods&&(' +
// unroll the `createElement` calls
getElements().join().replace(/\w+/g, function(nodeName) {
data.createElem(nodeName);
data.frag.createElement(nodeName);
return 'c("' + nodeName + '")';
}) +
');return n}'
)(html5, data.frag);
}
/*--------------------------------------------------------------------------*/
/**
* Shivs the given document.
* @memberOf html5
* @param {Document} ownerDocument The document to shiv.
* @returns {Document} The shived document.
*/
function shivDocument(ownerDocument) {
if (!ownerDocument) {
ownerDocument = document;
}
var data = getExpandoData(ownerDocument);
if (html5.shivCSS && !supportsHtml5Styles && !data.hasCSS) {
data.hasCSS = !!addStyleSheet(ownerDocument,
// corrects block display not defined in IE6/7/8/9
'article,aside,figcaption,figure,footer,header,hgroup,nav,section{display:block}' +
// adds styling not present in IE6/7/8/9
'mark{background:#FF0;color:#000}'
);
}
if (!supportsUnknownElements) {
shivMethods(ownerDocument, data);
}
return ownerDocument;
}
/*--------------------------------------------------------------------------*/
/**
* The `html5` object is exposed so that more elements can be shived and
* existing shiving can be detected on iframes.
* @type Object
* @example
*
* // options can be changed before the script is included
* html5 = { 'elements': 'mark section', 'shivCSS': false, 'shivMethods': false };
*/
var html5 = {
/**
* An array or space separated string of node names of the elements to shiv.
* @memberOf html5
* @type Array|String
*/
'elements': options.elements || 'abbr article aside audio bdi canvas data datalist details figcaption figure footer header hgroup mark meter nav output progress section summary time video',
/**
* A flag to indicate that the HTML5 style sheet should be inserted.
* @memberOf html5
* @type Boolean
*/
'shivCSS': (options.shivCSS !== false),
/**
* Is equal to true if a browser supports creating unknown/HTML5 elements
* @memberOf html5
* @type boolean
*/
'supportsUnknownElements': supportsUnknownElements,
/**
* A flag to indicate that the document's `createElement` and `createDocumentFragment`
* methods should be overwritten.
* @memberOf html5
* @type Boolean
*/
'shivMethods': (options.shivMethods !== false),
/**
* A string to describe the type of `html5` object ("default" or "default print").
* @memberOf html5
* @type String
*/
'type': 'default',
// shivs the document according to the specified `html5` object options
'shivDocument': shivDocument,
//creates a shived element
createElement: createElement,
//creates a shived documentFragment
createDocumentFragment: createDocumentFragment
};
/*--------------------------------------------------------------------------*/
// expose html5
window.html5 = html5;
// shiv the document
shivDocument(document);
}(this, document));
2、元素浮动之后,能设置宽度的话就给元素加宽度.如果需要宽度是内容撑开,就给它里边的块元素加上浮动
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title></title>
<style type="text/css">
.box{
width: 400px;
border: 1px solid #0000FF;
}
.clearfix{
zoom: 1;
}
.clearfix:after{
content: ".";
height: 0;
display: block;
visibility: hidden;
clear: both;
}
.left{
background: #FF0000;
float: left;
}
.right{
background: #EFFE00;
float: right;
}
h2{
float: left;
margin: 0;
height: 30px; 让浮动过的父级块中的子级元素，再浮动
}
</style>
<!--
在IE6下左右子级中的块元素设置高度后会撑开父级，并且独立各占一行
解决方案：让浮动过的父级块中的子级元素，再浮动，加样式，float: left;
-->
</head>
<body>
<div class="box clearfix">
<div class="left"><h2>今日标题</h2></div>
<div class="right"><h2>更多>></h2></div>
</div>
</body>
</html>
3、第一块元素浮动,第二块元素加margin值等于第一块元素,在IE6下会有间隙问题
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
body{
margin: 0;
}
.box{
width: 500px;
}
.left{
width: 200px;
height: 200px;
background-color: red;
float: left;
}
.right{
width: 200px;
height: 200px;
background-color: blue;
/*margin-left: 200px;*/ /*这里要注意,不用这种布局*/
float: left;
}
</style>
<!--
IE6下中间会出现空白缝隙
解决方案：
1、不建议一个元素浮动，另一个元素用margin-浮动方向：200px。这么写
2、直接用浮动，就不会出现这种问题解决
-->
</head>
<body>
<div class="box">
<div class="left"></div>
<div class="right"></div>
</div>
</body>
</html>
4、IE6下子元素超出父级宽高，会把父级的宽高撑开
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
.box{
width: 100px;
height: 100px;
border: 10px solid #000;
}
.content{
width: 200px;
height: 200px;
background-color: red;
}
</style>
<!--
解决方案：
不要让子元素的宽高超过父级
-->
</head>
<body>
<div class="box">
<div class="content"></div>
</div>
</body>
</html>
5、p 包含块元素嵌套规则
p标签 h标签 不要包含块元素
6、margin兼容性问题
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
.box{
background-color: green;
overflow: hidden;
zoom:1;
}
.item{
height: 50px;
background-color: red;
margin-top: 50px;
}
.mt100{
margin-top: 100px;
}
</style>
<!--
1、margin-top传递
触发BFC、haslayout，样式加 overflow: hidden;标准浏览器中可以解决问题，IE6中加 zoom:1；可以解决
2、上下margin叠压
尽量使用同一方向的margin，比如都设置top或者bottom，让一个margin：100px；
不要让一个margin-bottom：50px;另一个margin-top:50px,这种叠加方式
-->
</head>
<body>
<div class="box">
<div class="item"></div>
<div class="item mt100"></div>
</div>
</body>
</html>
7、display:inline-block
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
div{
width: 100px;
height: 100px;
background-color: red;
display: inline-block;
*display:inline;
*zoom:1;
}
</style>
<!--
IE6 并不支持 display: inline-block; 因为这个属性是CSS2.1出来的
解决方案是在样式中添加代码：
*display:inline;
*zoom:1;
-->
</head>
<body>
<div>div</div>
<div>div</div>
<div>div</div>
</body>
</html>
8、IE6 最小高度问题
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
div{
height: 1px;
background-color: red;
overflow: hidden; /*兼容IE6*/
}
</style>
<!--
IE6下最小高度19px，即便设置为1px，在IE6下也是19的高度
解决方案：
overflow:hidden;
-->
</head>
<body>
<div></div>
</body>
</html>
9、IE6 双边距
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
body{
margin: 0;
}
.box{
width: 750px;
border: 1px solid #000;
overflow: hidden;
}
.item{
width: 200px;
height: 200px;
background-color: red;
margin-left: 50px;
float: left;
/**display: inline;*/
}
</style>
<!--
当元素浮动后再设置margin那么就会产生双倍边距
解决方案：
针对ie6、7添加 display:inline 只针对IE添加 前面加个*号
-->
</head>
<body>
<div class="box">
<div class="item"></div>
<div class="item"></div>
<div class="item"></div>
</div>
</body>
</html>
IE6下的双边距，将块元素挤到下一行。
10、li 里元素都浮动 li 在IE6 7 下方会产生4px间隙问题
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
.list{
margin: 0;
padding: 0;
list-style: none;
width: 300px;
}
.list li{
height: 30px;
border: 1px solid red;
line-height: 30px;
/**vertical-align: top;*/
}
.list li a{
float: left;
}
.list li span{
float: right;
}
</style>
<!--
在IE6下 li 与 li 之间存在间隙
解决方案：
针对ie6，7添加vertical-align: top;
-->
</head>
<body>
<ul class="list">
<li>
<a href="">左边</a>
<span>右边</span>
</li>
<li>
<a href="">左边</a>
<span>右边</span>
</li>
<li>
<a href="">左边</a>
<span>右边</span>
</li>
<li>
<a href="">左边</a>
<span>右边</span>
</li>
</ul>
</body>
</html>
11、浮动元素之间注释，导致多复制一个文字问题
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
.wrap{
width: 400px;
}
.left{
float: left;
}
.right{
width: 398px;
float: right;
}
</style>
<!--
两个浮动元素中间有注释或者内联元素并且和父级宽度相差不超过3px的时候会出现“小尾巴”
解决方案：
1、两个浮动元素中间避免出现内联元素或者注释
2、与父级宽度相差3px或以上
-->
</head>
<body>
<div class="wrap">
<div class="left"></div>
<span></span><!-- IE下文字溢出BUG -->
<div class="right">↓这是多出来的一只猪</div>
</div>
</body>
</html>
12、IE6 7 父级元素的overflow:hidden 是包不住子级的relative
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
.box{
width: 200px;
height: 200px;
background-color: red;
border: 10px solid black;
overflow: hidden;
*position: relative; /* 针对ie6、7给父级元素添加相对定位 */
}
.content{
width: 400px;
height: 400px;
background-color: blue;
position: relative;
}
</style>
<!--
解决方案：
针对ie6、7给父级元素添加相对定位，让父级和子级处于一个相同的环境
-->
</head>
<body>
<div class="box">
<div class="content"></div>
</div>
</body>
</html>
13、IE6下绝对定位元素父级宽高是奇数,绝对定位元素的right和bottom值会有1px的偏差
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
.box{
width: 308px;
height: 308px;
background-color: red;
position: absolute;
}
.content{
width: 100px;
height: 100px;
background-color: blue;
position: absolute;
right: 0;
bottom: 0;
/*left:0;*/
/*top: 0; 对上和左并没有影响 */
}
</style>
<!--
解决方案：
避免父级宽高出现奇数
-->
</head>
<body>
<div class="box">
<div class="content"></div>
</div>
</body>
</html>
14、IE6下绝对定位元素和浮动元素并列，绝对定位元素消失
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
.box{
width: 200px;
height: 200px;
border: 1px solid black;
position: relative;
}
.item{
width: 150px;
height: 150px;
background-color: red;
float: left;
margin-left: 50px;
*display: inline;
}
.box span{
width: 50px;
height: 50px;
background-color: yellow;
position: absolute;
right: -10px;
top: -10px;
}
</style>
<!--
解决方案：
浮动元素和绝对定位元素是同级的话定位元素就会消失。所以咱们只要让他们俩不处于同级就可以避免这个bug。
-->
</head>
<body>
<div class="box">
<div class="item"></div>
<p>
<!--在这里原来的span标签是与<div class="item"></div>同级并列的，
但是为了去除IE6的不兼容，将span标签放入在p标签中了，这样二者就不是并列关系了，所以不兼容情况解决-->
<span></span>
</p>
</div>
</body>
</html>
15、IE6 下input的空隙
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
.box{
width: 200px;
border: 1px solid #000000;
background-color: red;
}
.box input{
border: 0;
margin: 0;
width: 200px;
height: 30px;
background-color: #fff;
*float: left; /*针对IE6 7增加个浮动*/
}
</style>
<!--
解决方案：
给input元素添加float
-->
</head>
<body>
<div class="box">
<input type="text" />
</div>
</body>
</html>
16、IE6 下 输入类型表单控件背景问题
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title></title>
<style type="text/css">
input{
/*当输入框存在背景图片的时候，随着输入背景图片也跟着移动，这个时候要使用fixed属性将背景图片固定*/
background: url("img/bg_icon.jpg") no-repeat fixed;
}
</style>
</head>
<body>
<input type="text">
<!--
解决办法：给背景添加 background-attachment: fixed; 属性
-->
</body>
</html>
二、CSS hack
hack 黑客？ （原意：修改）
针对不同的浏览器写不同的CSS 样式的过程，就叫CSS hack!
\9 所有的IE10及之前
* IE7及ie7以下的ie浏览器认识
_IE6及ie6的ie浏览器认识 远离css hack，有益身心健康！
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<style>
div{
width: 200px;
height: 200px;
background-color: red;
background-color: blue\9;
*background-color: green;
_background-color: yellow;
}
</style>
<!--
\9 （前面加 \9）IE10以及IE10以下版本的
* （前面加下星号）IE7以及IE7以下版本的
_（前面加下划线）IE6以及IE6以下版本的
-->
</head>
<body>
<div></div>
</body>
</html>
三、PNG24 兼容性问题
IE6不支持png24 图片。
两种方法：
方法1：调用JS
解决方案： JS插件(问题:不能处理body之上png24) DD_belatedPNG.fix('xxx');
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<script src="js/DD_belatedPNG_0.0.8a.js"></script>
<script>
DD_belatedPNG.fix("img, div");
</script>
<style>
body{
background-color: red;
}
div{
width: 300px;
height: 300px;
background: url("img/png.png") no-repeat;
}
</style>
</head>
<body>
<div></div>
<img src="img/png.png" alt="" />
</body>
</html>
/**
* DD_belatedPNG: Adds IE6 support: PNG images for CSS background-image and HTML <IMG/>.
* Author: Drew Diller
* Email: drew.diller@gmail.com
* URL: http://www.dillerdesign.com/experiment/DD_belatedPNG/
* Version: 0.0.8a
* Licensed under the MIT License: http://dillerdesign.com/experiment/DD_belatedPNG/#license
*
* Example usage:
* DD_belatedPNG.fix('.png_bg'); // argument is a CSS selector
* DD_belatedPNG.fixPng( someNode ); // argument is an HTMLDomElement
**/
/*
PLEASE READ:
Absolutely everything in this script is SILLY. I know this. IE's rendering of certain pixels doesn't make sense, so neither does this code!
*/
var DD_belatedPNG = {
ns: 'DD_belatedPNG',
imgSize: {},
delay: 10,
nodesFixed: 0,
createVmlNameSpace: function () { /* enable VML */
if (document.namespaces && !document.namespaces[this.ns]) {
document.namespaces.add(this.ns, 'urn:schemas-microsoft-com:vml');
}
},
createVmlStyleSheet: function () { /* style VML, enable behaviors */
/*
Just in case lots of other developers have added
lots of other stylesheets using document.createStyleSheet
and hit the 31-limit mark, let's not use that method!
further reading: http://msdn.microsoft.com/en-us/library/ms531194(VS.85).aspx
*/
var screenStyleSheet, printStyleSheet;
screenStyleSheet = document.createElement('style');
screenStyleSheet.setAttribute('media', 'screen');
document.documentElement.firstChild.insertBefore(screenStyleSheet, document.documentElement.firstChild.firstChild);
if (screenStyleSheet.styleSheet) {
screenStyleSheet = screenStyleSheet.styleSheet;
screenStyleSheet.addRule(this.ns + '\\:*', '{behavior:url(#default#VML)}');
screenStyleSheet.addRule(this.ns + '\\:shape', 'position:absolute;');
screenStyleSheet.addRule('img.' + this.ns + '_sizeFinder', 'behavior:none; border:none; position:absolute; z-index:-1; top:-10000px; visibility:hidden;'); /* large negative top value for avoiding vertical scrollbars for large images, suggested by James O'Brien, http://www.thanatopsic.org/hendrik/ */
this.screenStyleSheet = screenStyleSheet;
/* Add a print-media stylesheet, for preventing VML artifacts from showing up in print (including preview). */
/* Thanks to R�mi Pr�vost for automating this! */
printStyleSheet = document.createElement('style');
printStyleSheet.setAttribute('media', 'print');
document.documentElement.firstChild.insertBefore(printStyleSheet, document.documentElement.firstChild.firstChild);
printStyleSheet = printStyleSheet.styleSheet;
printStyleSheet.addRule(this.ns + '\\:*', '{display: none !important;}');
printStyleSheet.addRule('img.' + this.ns + '_sizeFinder', '{display: none !important;}');
}
},
readPropertyChange: function () {
var el, display, v;
el = event.srcElement;
if (!el.vmlInitiated) {
return;
}
if (event.propertyName.search('background') != -1 || event.propertyName.search('border') != -1) {
DD_belatedPNG.applyVML(el);
}
if (event.propertyName == 'style.display') {
display = (el.currentStyle.display == 'none') ? 'none' : 'block';
for (v in el.vml) {
if (el.vml.hasOwnProperty(v)) {
el.vml[v].shape.style.display = display;
}
}
}
if (event.propertyName.search('filter') != -1) {
DD_belatedPNG.vmlOpacity(el);
}
},
vmlOpacity: function (el) {
if (el.currentStyle.filter.search('lpha') != -1) {
var trans = el.currentStyle.filter;
trans = parseInt(trans.substring(trans.lastIndexOf('=')+1, trans.lastIndexOf(')')), 10)/100;
el.vml.color.shape.style.filter = el.currentStyle.filter; /* complete guesswork */
el.vml.image.fill.opacity = trans; /* complete guesswork */
}
},
handlePseudoHover: function (el) {
setTimeout(function () { /* wouldn't work as intended without setTimeout */
DD_belatedPNG.applyVML(el);
}, 1);
},
/**
* This is the method to use in a document.
* @param {String} selector - REQUIRED - a CSS selector, such as '#doc .container'
**/
fix: function (selector) {
if (this.screenStyleSheet) {
var selectors, i;
selectors = selector.split(','); /* multiple selectors supported, no need for multiple calls to this anymore */
for (i=0; i<selectors.length; i++) {
this.screenStyleSheet.addRule(selectors[i], 'behavior:expression(DD_belatedPNG.fixPng(this))'); /* seems to execute the function without adding it to the stylesheet - interesting... */
}
}
},
applyVML: function (el) {
el.runtimeStyle.cssText = '';
this.vmlFill(el);
this.vmlOffsets(el);
this.vmlOpacity(el);
if (el.isImg) {
this.copyImageBorders(el);
}
},
attachHandlers: function (el) {
var self, handlers, handler, moreForAs, a, h;
self = this;
handlers = {resize: 'vmlOffsets', move: 'vmlOffsets'};
if (el.nodeName == 'A') {
moreForAs = {mouseleave: 'handlePseudoHover', mouseenter: 'handlePseudoHover', focus: 'handlePseudoHover', blur: 'handlePseudoHover'};
for (a in moreForAs) {
if (moreForAs.hasOwnProperty(a)) {
handlers[a] = moreForAs[a];
}
}
}
for (h in handlers) {
if (handlers.hasOwnProperty(h)) {
handler = function () {
self[handlers[h]](el);
};
el.attachEvent('on' + h, handler);
}
}
el.attachEvent('onpropertychange', this.readPropertyChange);
},
giveLayout: function (el) {
el.style.zoom = 1;
if (el.currentStyle.position == 'static') {
el.style.position = 'relative';
}
},
copyImageBorders: function (el) {
var styles, s;
styles = {'borderStyle':true, 'borderWidth':true, 'borderColor':true};
for (s in styles) {
if (styles.hasOwnProperty(s)) {
el.vml.color.shape.style[s] = el.currentStyle[s];
}
}
},
vmlFill: function (el) {
if (!el.currentStyle) {
return;
} else {
var elStyle, noImg, lib, v, img, imgLoaded;
elStyle = el.currentStyle;
}
for (v in el.vml) {
if (el.vml.hasOwnProperty(v)) {
el.vml[v].shape.style.zIndex = elStyle.zIndex;
}
}
el.runtimeStyle.backgroundColor = '';
el.runtimeStyle.backgroundImage = '';
noImg = true;
if (elStyle.backgroundImage != 'none' || el.isImg) {
if (!el.isImg) {
el.vmlBg = elStyle.backgroundImage;
el.vmlBg = el.vmlBg.substr(5, el.vmlBg.lastIndexOf('")')-5);
}
else {
el.vmlBg = el.src;
}
lib = this;
if (!lib.imgSize[el.vmlBg]) { /* determine size of loaded image */
img = document.createElement('img');
lib.imgSize[el.vmlBg] = img;
img.className = lib.ns + '_sizeFinder';
img.runtimeStyle.cssText = 'behavior:none; position:absolute; left:-10000px; top:-10000px; border:none; margin:0; padding:0;'; /* make sure to set behavior to none to prevent accidental matching of the helper elements! */
imgLoaded = function () {
this.width = this.offsetWidth; /* weird cache-busting requirement! */
this.height = this.offsetHeight;
lib.vmlOffsets(el);
};
img.attachEvent('onload', imgLoaded);
img.src = el.vmlBg;
img.removeAttribute('width');
img.removeAttribute('height');
document.body.insertBefore(img, document.body.firstChild);
}
el.vml.image.fill.src = el.vmlBg;
noImg = false;
}
el.vml.image.fill.on = !noImg;
el.vml.image.fill.color = 'none';
el.vml.color.shape.style.backgroundColor = elStyle.backgroundColor;
el.runtimeStyle.backgroundImage = 'none';
el.runtimeStyle.backgroundColor = 'transparent';
},
/* IE can't figure out what do when the offsetLeft and the clientLeft add up to 1, and the VML ends up getting fuzzy... so we have to push/enlarge things by 1 pixel and then clip off the excess */
vmlOffsets: function (el) {
var thisStyle, size, fudge, makeVisible, bg, bgR, dC, altC, b, c, v;
thisStyle = el.currentStyle;
size = {'W':el.clientWidth+1, 'H':el.clientHeight+1, 'w':this.imgSize[el.vmlBg].width, 'h':this.imgSize[el.vmlBg].height, 'L':el.offsetLeft, 'T':el.offsetTop, 'bLW':el.clientLeft, 'bTW':el.clientTop};
fudge = (size.L + size.bLW == 1) ? 1 : 0;
/* vml shape, left, top, width, height, origin */
makeVisible = function (vml, l, t, w, h, o) {
vml.coordsize = w+','+h;
vml.coordorigin = o+','+o;
vml.path = 'm0,0l'+w+',0l'+w+','+h+'l0,'+h+' xe';
vml.style.width = w + 'px';
vml.style.height = h + 'px';
vml.style.left = l + 'px';
vml.style.top = t + 'px';
};
makeVisible(el.vml.color.shape, (size.L + (el.isImg ? 0 : size.bLW)), (size.T + (el.isImg ? 0 : size.bTW)), (size.W-1), (size.H-1), 0);
makeVisible(el.vml.image.shape, (size.L + size.bLW), (size.T + size.bTW), (size.W), (size.H), 1 );
bg = {'X':0, 'Y':0};
if (el.isImg) {
bg.X = parseInt(thisStyle.paddingLeft, 10) + 1;
bg.Y = parseInt(thisStyle.paddingTop, 10) + 1;
}
else {
for (b in bg) {
if (bg.hasOwnProperty(b)) {
this.figurePercentage(bg, size, b, thisStyle['backgroundPosition'+b]);
}
}
}
el.vml.image.fill.position = (bg.X/size.W) + ',' + (bg.Y/size.H);
bgR = thisStyle.backgroundRepeat;
dC = {'T':1, 'R':size.W+fudge, 'B':size.H, 'L':1+fudge}; /* these are defaults for repeat of any kind */
altC = { 'X': {'b1': 'L', 'b2': 'R', 'd': 'W'}, 'Y': {'b1': 'T', 'b2': 'B', 'd': 'H'} };
if (bgR != 'repeat' || el.isImg) {
c = {'T':(bg.Y), 'R':(bg.X+size.w), 'B':(bg.Y+size.h), 'L':(bg.X)}; /* these are defaults for no-repeat - clips down to the image location */
if (bgR.search('repeat-') != -1) { /* now let's revert to dC for repeat-x or repeat-y */
v = bgR.split('repeat-')[1].toUpperCase();
c[altC[v].b1] = 1;
c[altC[v].b2] = size[altC[v].d];
}
if (c.B > size.H) {
c.B = size.H;
}
el.vml.image.shape.style.clip = 'rect('+c.T+'px '+(c.R+fudge)+'px '+c.B+'px '+(c.L+fudge)+'px)';
}
else {
el.vml.image.shape.style.clip = 'rect('+dC.T+'px '+dC.R+'px '+dC.B+'px '+dC.L+'px)';
}
},
figurePercentage: function (bg, size, axis, position) {
var horizontal, fraction;
fraction = true;
horizontal = (axis == 'X');
switch(position) {
case 'left':
case 'top':
bg[axis] = 0;
break;
case 'center':
bg[axis] = 0.5;
break;
case 'right':
case 'bottom':
bg[axis] = 1;
break;
default:
if (position.search('%') != -1) {
bg[axis] = parseInt(position, 10) / 100;
}
else {
fraction = false;
}
}
bg[axis] = Math.ceil( fraction ? ( (size[horizontal?'W': 'H'] * bg[axis]) - (size[horizontal?'w': 'h'] * bg[axis]) ) : parseInt(position, 10) );
if (bg[axis] % 2 === 0) {
bg[axis]++;
}
return bg[axis];
},
fixPng: function (el) {
el.style.behavior = 'none';
var lib, els, nodeStr, v, e;
if (el.nodeName == 'BODY' || el.nodeName == 'TD' || el.nodeName == 'TR') { /* elements not supported yet */
return;
}
el.isImg = false;
if (el.nodeName == 'IMG') {
if(el.src.toLowerCase().search(/\.png$/) != -1) {
el.isImg = true;
el.style.visibility = 'hidden';
}
else {
return;
}
}
else if (el.currentStyle.backgroundImage.toLowerCase().search('.png') == -1) {
return;
}
lib = DD_belatedPNG;
el.vml = {color: {}, image: {}};
els = {shape: {}, fill: {}};
for (v in el.vml) {
if (el.vml.hasOwnProperty(v)) {
for (e in els) {
if (els.hasOwnProperty(e)) {
nodeStr = lib.ns + ':' + e;
el.vml[v][e] = document.createElement(nodeStr);
}
}
el.vml[v].shape.stroked = false;
el.vml[v].shape.appendChild(el.vml[v].fill);
el.parentNode.insertBefore(el.vml[v].shape, el);
}
}
el.vml.image.shape.fillcolor = 'none'; /* Don't show blank white shapeangle when waiting for image to load. */
el.vml.image.fill.type = 'tile'; /* Makes image show up. */
el.vml.color.fill.on = false; /* Actually going to apply vml element's style.backgroundColor, so hide the whiteness. */
lib.attachHandlers(el);
lib.giveLayout(el);
lib.giveLayout(el.offsetParent);
el.vmlInitiated = true;
lib.applyVML(el); /* Render! */
}
};
try {
document.execCommand("BackgroundImageCache", false, true); /* TredoSoft Multiple IE doesn't like this, so try{} it */
} catch(r) {}
DD_belatedPNG.createVmlNameSpace();
DD_belatedPNG.createVmlStyleSheet();
方法2：
原生滤镜 _background:none;_filter : progid:DXImageTransform.Microsoft.AlphaImageLoader(src="XX.png", sizingMethod="crop");
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<script src="js/DD_belatedPNG_0.0.8a.js"></script>
<script>
DD_belatedPNG.fix("body");
</script>
<style>
body{
width: 500px;
height: 500px;
background:red url("img/png.png") no-repeat;
_background-image:none;
_filter : progid:DXImageTransform.Microsoft.AlphaImageLoader(src="img/png.png", sizingMethod="crop");
}
</style>
</head>
<body>
</body>
</html>
四、样式优先级、提升样式优先级
默认 < 类型 < class < id < style(行间) < !important
!important 提升样式优先级权重
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