Simple javascript include

include.js

function include(url) {
    var element;
    switch (url.split(".").pop()) {
    case "css":
        {
            element = document.createElement("link");
            element.setAttribute("rel", "stylesheet");
            element.setAttribute("type", "text/css")
            element.setAttribute("href", url)
        }
        break;
    case "js":
        {
            element = document.createElement("script");
            element.setAttribute("language", "javascript")
            element.setAttribute("src", url)
        }
        break;
    default:
        window.console && window.console.error("could not identify", url, "skip include");
        return;
    }
    var head = document.querySelector("head");
    if (head.innerHTML.indexOf(element.outerHTML) != -1) {
        window.console && window.console.warn("Duplicate include, skipping:", url);
    } else {
        head.appendChild(element);
    }
}