<! doctype html > < html lang = "en" > < head > <!-- Required meta tags --> < meta charset = "utf-8" > < meta name = "viewport" content = "width=device-width, initial-scale=1, shrink-to-fit=no" > <!-- Bootstrap CSS --> < link rel = "stylesheet" href = "https://stackpath.bootstrapcdn.com/bootstrap/4.5.0/css/bootstrap.min.css" integrity = "sha384-9aIt2nRpC12Uk9gS9baDl411NQApFmC26EwAOH8WgZl5MYYxFfc+NcPb1dKGj7Sk" crossorigin = "anonymous" > < title > Hello, world! </ title > < script > setInterval (() => { ...