动态加载、移除、替换JS和CSS

//动态加载一个js/css文件
function loadjscssfile(filename, filetype) {
if (filetype == "js") {
var fileref = document.createElement('script')
fileref.setAttribute("type", "text/javascript")
fileref.setAttribute("src", filename)
}
else if (filetype == "css") {
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)
}

//移动已经加载过的js/css
function removejscssfile(filename, filetype) {
var targetelement = (filetype == "js") ? "script" : (filetype == "css") ? "link" : "none"
var targetattr = (filetype == "js") ? "src" : (filetype == "css") ? "href" : "none"
var allsuspects = document.getElementsByTagName(targetelement)
for (var i = allsuspects.length; i >= 0; i--) {
if (allsuspects[i] && allsuspects[i].getAttribute(targetattr) != null && allsuspects[i].getAttribute(targetattr).indexOf(filename) != -1)
allsuspects[i].parentNode.removeChild(allsuspects[i])
}
}