improve_bouncerate.js

(function(w, d, ga){

        var longStay = 0, scrollsDeep;

        // Check how deep down the page a user has scrolled
        function getScrollPercent() {
            var h = document.documentElement,
                b = document.body,
                st = 'scrollTop',
                sh = 'scrollHeight';
            return Math.floor((h[st]||b[st]) / ((h[sh]||b[sh]) - h.clientHeight) * 100);
        }

        function fireEvent() {

            // We only fire an event if GA is loaded and if either the visitor is more than 5 seconds on the page or
            // if he has scrolled more 25% deep but not when both conditions occured

            if (ga && (longStay || scrollsDeep) && !(longStay && scrollsDeep)) {
                ga('send', {
                    hitType: "event",
                    eventCategory: "bounce",
                    eventAction: "interaction",
                })
            }
        }

        // Listen to scroll events and fire an event if the user reaches 25% but not when it already has fired
        d.addEventListener("scroll", function() {
            if (getScrollPercent() > 25 && !scrollsDeep) {
                scrollsDeep = 1;
                fireEvent();
            }
        })

        // If the user stays on the page for more than 5 seconds
        setTimeout(function() {
            longStay = 1;
            fireEvent();
        }, 5000)
    
})(window, document, ga);