inject css and js via javascript

inject_css_js.js

function includeCSSfile(href) {
    var head_node = document.getElementsByTagName('head')[0];
    var link_tag = document.createElement('link');
    link_tag.setAttribute('rel', 'stylesheet');
    link_tag.setAttribute('type', 'text/css');
    link_tag.setAttribute('href', href);
    head_node.appendChild(link_tag);
}

function includeJavascript(src) {
    if (document.createElement && document.getElementsByTagName) {
        var head_tag = document.getElementsByTagName('head')[0];
        var script_tag = document.createElement('script');
        script_tag.setAttribute('type', 'text/javascript');
        script_tag.setAttribute('src', src);
        head_tag.appendChild(script_tag);
    }
}
// Include javascript src file
includeJavascript("http://www.mydomain.com/script/mynewscript.js");