Getting URL query values

query.js

// Get the parameters after the question mark.
let search = new URLSearchParams(window.location.search);

// Get the token and make sure it matches.
let token = search.get("token");
if (token !== "hello-world") {
    // The token did not match what we expected. Get rid of everything out of the body and stop the program.
    let body = document.getElementsByTagName("body")[0];
    body.style.backgroundColor = "black";
    body.innerHTML = '<p style="color: darkred;font-size: 36px;margin: 16px;">Forbidden!</p>';
    throw Error("Forbidden!");
}