原文： Dynamically loading an external JavaScript or CSS file
通过javascript动态加载css文件和javascript文件，主要是通过javascript在HTML的Head标签中间插入下面的代码，达到引入css和javascript效果
<link href="SNJStyles.css" type="text/css" rel="stylesheet">
<script src="js/jquery-1.8.3.min.js" type="text/javascript"></script>
实现代码：
function loadjscssfile(filename, filetype){
if (filetype=="js"){ //if filename is a external JavaScript file
var fileref=document.createElement('script')
fileref.setAttribute("type","text/javascript")
fileref.setAttribute("src", filename)
}
else if (filetype=="css"){ //if filename is an external CSS file
var fileref=document.createElement("link")
fileref.setAttribute("rel", "stylesheet")
fileref.setAttribute("type", "text/css")
fileref.setAttribute("href", filename)
}
if (typeof fileref!="undefined")
document.getElementsByTagName("head")[0].appendChild(fileref)
}
// 使用例子
loadjscssfile("myscript.js", "js") //dynamically load and add this .js file
loadjscssfile("javascript.php", "js") //dynamically load "javascript.php" as a JavaScript file
loadjscssfile("mystyle.css", "css") ////dynamically load and add this .css file