For this code I am using cookies to save the value every time the website refreshes.
const _ = {
    cookie_class: class cookies {
        constructor() {
        }
        setCookie(cookie_name, cookie_value, expire_in_days) {
            var d = new Date();
            d.setTime(d.getTime() + (expire_in_days * 24 * 60 * 60 * 1000));
            var expires = "expires=" + d.toUTCString();
            document.cookie = cookie_name + "=" + cookie_value + ";" + expires + ";path=/";
        }
        getCookie(cookie_name) {
            var name = cookie_name + "=";
            var ca = document.cookie.split(';');
            for (var i = 0; i < ca.length; i++) {
                var c = ca[i];
                while (c.charAt(0) == ' ') {
                    c = c.substring(1);
                }
                if (c.indexOf(name) == 0) {
                    return c.substring(name.length, c.length);
                }
            }
            return "";
        }
        exists(cookie) {
            var user = this.getCookie(cookie);
            if (user != "") {
                return true;
            } else {
                return false;
            }
        }
    }
}
const cookies = new _.cookie_class();
let interval;
const refresh = () => {
    location.reload();
}
let cookie_name = "refresh_interval";
window.onload = () => {
    if (cookies.exists(cookie_name)) {
        interval = setInterval(refresh, parseInt(cookies.getCookie(cookie_name)));
    }
}
const update = () => {
    let value = document.getElementById('input').value;
    if (!isNaN(parseInt(value))) {
        cookies.setCookie(cookie_name, parseInt(value), 365);
        clearInterval(interval);
        interval = setInterval(refresh, parseInt(value));
    } else {
        // Handle is however you would Like:
        // The input is not a Number
    }
};
// Listeners
document.getElementById('apply-btn').addEventListener('click', (event) => {
    event.preventDefault();
    update();
});
Tell me if it works for you!