ScrollTrack.js

<script>
    
    // ScrollTrack.js allows a function to be run once and only once if it's seen.
    // Ben Yanke <ben@benyanke.com>

    // SelectorToWatch - a standard jquery element selector
    // functionToRun - a function to be run when the selector is on screen
    function scrollWatch(selectorToWatch, functionToRun) {

        
        // Check first to see if it even exists on the page
        if (!$(selectorToWatch).position()) {
            return false;
        } else {
            console.log(selectorToWatch + " found: binding to scroll events");
        }

        // Check the first time
        if (checkIfOnScreen(selectorToWatch)) {

            functionToRun();

        } else {
            // If it's not there right away, check on every scroll

            // Run this on every scroll event
            var scroller = $(document).on('scroll', function() {

                // If the tracked div is in the window, fire event
                if (checkIfOnScreen(selectorToWatch)) {

                    // Any code in here will be run once and only once if the element is scrolled to
                    console.log("The selector '" + selectorToWatch + "' scrolled into view. Unbinding listener");
                    functionToRun();

                    // Ensures this never runs multiple times by unbinding the scroll event listener
                    scroller.unbind();
                }
            });
        }


        function checkIfOnScreen(selectorToWatch) {

            var top_of_selectorToWatch = $(selectorToWatch).offset().top;
            var bottom_of_selectorToWatch = $(selectorToWatch).offset().top + $(selectorToWatch).outerHeight();
            var bottom_of_screen = $(window).scrollTop() + $(window).height();
            var top_of_screen = $(window).scrollTop();

            if ((bottom_of_screen > top_of_selectorToWatch) && (top_of_screen < bottom_of_selectorToWatch)) {
                return true;
            } else {
                return false;
            }

        }

    }


    function trackWrapper(element, title, callback) {
        scrollWatch(element, function() {
		
            // Send event to Google Analytics via Google Tag Manager - replace this with a ga() function if not in GTM
            dataLayer.push({
              'event': 'gaEvent',
              'gaEventName': 'ScrollTo: ' + title
            });
            
        });
    }


    trackWrapper('body.page-id-12775 #cutaway', '/displays/#cutaway');
    trackWrapper('body.page-id-12549 #Metal-Models', '/specialty-models/#Metal-Models');
    trackWrapper('body.page-id-12723 #mobile', '/cgi/#mobile');
          

</script>