pub fn eventlistener_keyboardevent_keydown(){
    let window = web_sys::window().expect("global window does not exists");    
    let document = window.document().expect("expecting a document on window");

    let text_area = document.get_element_by_id("text_area")
                            .unwrap()
                            .dyn_into::<web_sys::HtmlTextAreaElement>()
                            .unwrap();

    let message = document.get_element_by_id("message")
                            .unwrap()
                            .dyn_into::<web_sys::HtmlParagraphElement>()
                            .unwrap();

    let on_keydown = EventListener::new(&text_area, "keydown", move |event| {

    let keyboard_event = event.clone()
                        .dyn_into::<web_sys::KeyboardEvent>()
                        .unwrap();

            let mut event_string = String::from("");
            event_string.push_str(&event.type_());
            event_string.push_str(&" : ");
            event_string.push_str(&keyboard_event.key());
            
            message.set_text_content(Some(&event_string));
    
    });

    on_keydown.forget();     
    
}