实现原理，基于link标签的disable。
代码：
<!DOCTYPE />
<html>
<head>
<meta charset="utf-8">
<title>setTimeout</title>
<link class="codestyle" rel="prefetch alternate stylesheet" href="./c1.css">
<link class="codestyle" rel="prefetch alternate stylesheet" href="./c2.css">
<script type="text/javascript">
//link 切换
var style = 'c1';
function initSnippet() {
for (let link of document.querySelectorAll('.codestyle')) {
link.rel = 'stylesheet';
link.disabled = !link.href.match(style + '\\.css$'); //正则中"."需要转义，加个"\","\"又需要转义
}
}
addEventListener('load', initSnippet);
setTimeout(function () {
style = "c2";
initSnippet();
}, 1000)
</script>
</head>
<body>
<div style="width: 100px;height: 100px;"></div>
</body>
</html>
c1.css
div {
background-color: #f00;
}
c2.css
div {
background-color: #0f0;
}
