动态加载css和javascript

//dynamically loading .js or .css file 
function loadjscssfile(filename, filetype){
    var fileref;
    if (filetype=="js"){ //if filename is a external JavaScript file
        fileref = document.createElement('script');
        fileref.setAttribute("type","text/javascript");
        fileref.setAttribute("src", filename);
    }
    else if (filetype=="css"){ //if filename is an external CSS file
        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);
}