要判断这个 CSS 文件是否加载完毕,各个浏览器的做法差异比较大,这次要说IE浏览器做的不错,我们可以直接通过onload方法来处理CSS加载完成以后的处理:
复制代码 代码如下:
// 代码节选至seajs
function styleOnload(node, callback) {
// for IE6-9 and Opera
if (node.attachEvent) {
node.attachEvent('onload', callback);
// NOTICE:
// 1. "onload" will be fired in IE6-9 when the file is 404, but in
// this situation, Opera does nothing, so fallback to timeout.
// 2. "onerror" doesn't fire in any browsers!
}
}
很遗憾,这次在其他的浏览器中,想判断CSS是否加载完成就不是那么方便了,FF,webkit可以通过node.sheet.cssRules属性是否存在来判断是否加载完毕。而且需要使用setTimeout间隔事件轮询:
复制代码 代码如下:
// 代码节选至seajs
function poll(node, callback) {
if (callback.isCalled) {
return;
}
var isLoaded = false;
if (/webkit/i.test(navigator.userAgent)) {//webkit
if (node['sheet']) {
isLoaded = true;
}
}
// for Firefox
else if (node['sheet']) {
try {
if (node['sheet'].cssRules) {
isLoaded = true;
}
} catch (ex) {
// NS_ERROR_DOM_SECURITY_ERR
if (ex.code === 1000) {
isLoaded = true;
}
}
}
if (isLoaded) {
// give time to render.
setTimeout(function() {
callback();
}, 1);
}
else {
setTimeout(function() {
poll(node, callback);
}, 1);
}
}
setTimeout(function() {
poll(node, callback);
}, 0);
SeaJS给出的完整的处理是这样的:
复制代码 代码如下:
function styleOnload(node, callback) {
// for IE6-9 and Opera
if (node.attachEvent) {
node.attachEvent('onload', callback);
// NOTICE:
// 1. "onload" will be fired in IE6-9 when the file is 404, but in
// this situation, Opera does nothing, so fallback to timeout.
// 2. "onerror" doesn't fire in any browsers!
}
// polling for Firefox, Chrome, Safari
else {
setTimeout(function() {
poll(node, callback);
}, 0); // for cache
}
}
function poll(node, callback) {
if (callback.isCalled) {
return;
}
var isLoaded = false;
if (/webkit/i.test(navigator.userAgent)) {//webkit
if (node['sheet']) {
isLoaded = true;
}
}
// for Firefox
else if (node['sheet']) {
try {
if (node['sheet'].cssRules) {
isLoaded = true;
}
} catch (ex) {
// NS_ERROR_DOM_SECURITY_ERR
if (ex.code === 1000) {
isLoaded = true;
}
}
}
if (isLoaded) {
// give time to render.
setTimeout(function() {
callback();
}, 1);
}
else {
setTimeout(function() {
poll(node, callback);
}, 1);
}
}
// 我的动态创建LINK函数
function createLink(cssURL,lnkId,charset,media){
var head = document.getElementsByTagName('head')[0],
linkTag = null;
if(!cssURL){
return false;
}
linkTag = document.createElement('link');
linkTag.setAttribute('id',(lnkId || 'dynamic-style'));
linkTag.setAttribute('rel','stylesheet');
linkTag.setAttribute('charset',(charset || 'utf-8'));
linkTag.setAttribute('media',(media||'all'));
linkTag.setAttribute('type','text/css');
linkTag.href = cssURL;
head.appendChild(linkTag);
}
function loadcss(){
var styleNode = createLink('/wp-content/themes/BlueNight/style.css');
styleOnload(styleNode,function(){
alert("loaded");
});
}
在看到seajs的代码的时候,我立刻想起了我看到Diego Perini的另一个解决方案:
复制代码 代码如下: