function set_display() {
    source_type = document.getElementsByTagName("select")[0];
    url_section = document.getElementsByClassName("url")[0]
    text_section = document.getElementsByClassName("text")[0]
    if (source_type.value == "url") {
        url_section.removeAttribute("hidden")
        text_section.setAttribute("hidden", "hidden")
    } else if (source_type.value == "text") {
        text_section.removeAttribute("hidden")
        url_section.setAttribute("hidden", "hidden")        
    }
}

function load() {
    document.getElementsByTagName("select")[0].addEventListener("change", set_display, false);
    set_display();
}

document.addEventListener("DOMContentLoaded", load, false);