user-idle-timeout

//initialize the function once the page loads
window.onload = function() {
            activateTimer();
        }

//show the popup if the user is idle for more than 15 seconds

// the user is considered idle if he doesn't actively interact 
//with the page by either moving his cursor or pressing any button on the keyboard
    const activateTimer = ()=> {
        let time;
        window.onload = resetTimer;
        document.onmousemove = resetTimer;
        document.onkeydown = resetTimer;

        function popSomething() {
            alert("show popup now")
        }

        function resetTimer() {
            clearTimeout(time);
            time = setTimeout(popSomething, 10000)
            }
        };