Ways to add javascript files dynamically in a page

Question

I have seen Scriptaculous.js file to include its required javascript files dynamically. Is there any better approach to include javascript dynamically.

For example,

Answer 1

document.getElementsByTagName("head")[0].appendChild(fileref‌​) is not working if you have some document.ready() works inline. $("head").append(fileref); works great for me, although it needs jquery.min.js inline reference.

and master_load.js :

function loadjscssfile(filename) {
    if (filename.substr(filename.length - 4) == ".css") { // 'endsWith' is not IE supported.
        var fileref = document.createElement("link")
        fileref.setAttribute("rel", "stylesheet")
        fileref.setAttribute("href", filename)
        //fileref.setAttribute("type", "text/css")
    }
    else if (filename.substr(filename.length - 3) == ".js") {
        var fileref = document.createElement('script')
        fileref.setAttribute("src", filename)
        //fileref.setAttribute("type", "text/javascript")
    }
    $("head").append(fileref);
}
function load_master_css() {
    loadjscssfile("css/bootstrap.min.css");
    // bunch of css files
}
function load_master_js() {
    loadjscssfile("script/bootstrap.min.js");
    // bunch of js files
}