JavaScript でアイドル時間を検出してコンテンツの読み込みを最適化するにはどうすればよいですか?

var inactivityTime = function () {
    var time;
    // Reset inactivity timer on page load and DOM events
    window.onload = resetTimer;
    document.onmousemove = resetTimer;
    document.onkeydown = resetTimer;

    function logout() {
        // Log out or perform any desired action upon idle time
        alert("You are now logged out.")
    }

    function resetTimer() {
        // Clear the timeout and set a new one for the idle time period
        clearTimeout(time);
        time = setTimeout(logout, 3000);
    }
};

window.onload = function() {
  inactivityTime();
}

document.onload
document.onmousemove
document.onmousedown
document.ontouchstart
document.onclick
document.onkeydown

window.addEventListener('load', resetTimer, true);
var events = ['mousedown', 'mousemove', 'keypress', 'scroll', 'touchstart'];
events.forEach(function(name) {
 document.addEventListener(name, resetTimer, true);
});