How to redirect page if login is not in Local Storage?

How can I redirect if the login is not done?
I'm starting in js and I'm still having difficulty with basic things...
I'm using Blogger, I've tried a few times, but I haven't been successful.

And in addition, I wanted to create a logout button to remove from local storage

This is login code + local storage:

<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-js -->

var storeS = localStorage.getItem("users");
if (storeS == null) {
var users = [{
username: "test",
password: "1234"
}];
localStorage.setItem("users", JSON.stringify(users));
}
function getUserUsername(username) {
return JSON.parse(localStorage.getItem('users')).filter(users => users.username === username)
}
function cheklog() {
var login = localStorage.getItem("login");
if (login != null && login == "true") {
document.querySelector(".wendyloginwrap").classList.add("hidden");
}
}
cheklog();
function startlog() {
var username = document.querySelector("#username").value;
var password = document.querySelector("#password").value;
if (getUserUsername(username.trim()).length > 0) {
var user = getUserUsername(username.trim())[0];
if (user.password == password.trim()) {
document.querySelector("#login-area").classList.add("hidden");
document.querySelector("#login-true").classList.remove("hidden");
localStorage.setItem("login", "true");
setTimeout(function() {
window.location.href = "#";
}, 2000);
} else {
document.querySelector("#akses").innerHTML = "username or password is invalid!";
}
} else {
document.querySelector("#akses").innerHTML = "username not found";
}
}
const show = () => {
var password = document.querySelector("#password");
var sandi = document.querySelector(".icon1");
var sandidua = document.querySelector(".icon2");
if (password.type === "password") {
password.type = "text";
sandidua.style.opacity = "1";
sandi.style.opacity = "0";
} else {
password.type = "password";
sandidua.style.opacity = "0";
sandi.style.opacity = "1";
}
}

<!-- end snippet -->

If you want to redirect the user to the login page you can simply use window.location.href or window.location.assign() but the check must be done on the "x" page you want to protect, like if (localStorage.getItem("login") !== "true") //redirect to login. For the logout button you can redirect as well and you can clear the local storage with localStorage.clear() (remove everythings) or localStorage.removeItem(item).