Auto dark-mode toggle

function checkTime() {
    var timeNow = new Date().getHours();
    const night = timeNow >= 16 || timeNow <= 7;
    return [timeNow, night];
}
function autoToggleNightMode() {
    const bodyClass = document.body.classList;
    var myinput = document.getElementsByClassName("switch")[0].getElementsByTagName("input")[0];
    var currentTime = checkTime()[0];
    var nightHours = checkTime()[1];
    if (document.cookie.indexOf("linx_dark") !== -1) {
        clearInterval(checkNightMode);
        return false;
    }
    if (nightHours === true) {
        myinput.setAttribute("checked", "checked");
        bodyClass.contains("dark-mode") === false ? bodyClass.add("dark-mode") : null;
        console.log("I've defined hour " + currentTime + " of the day as part of the 'night', so I'm automatically toggling night mode on for you!");
    } else {
        myinput.hasAttribute("checked") ? myinput.removeAttribute("checked") : null;
        bodyClass.contains("dark-mode") === true ? bodyClass.remove("dark-mode") : null;
        console.log("It's not night time anymore!!");
    }
}
autoToggleNightMode();
var checkNightMode = setInterval(autoToggleNightMode, 30000);

I want/need to put this behind a user checkbox, rather than straight up automated