This example gets the body HtmlElement, dynamically cast the element into a HtmlBodyElement, and use it to set the bgColor of the body.
pub fn document_body()
{
let window = web_sys::window().expect("global window does not exists");
let document = window.document().expect("expecting a document on window");
let body = document.body().expect("document expect to have have a body");
let val = body
.dyn_into::<web_sys::HtmlBodyElement>()
.unwrap();
val.set_bg_color("lightblue");
}
pub fn body(&self)-> Option<HtmlElement>