Scroll tracking trigger to check if page height is bigger than the double of your viewport (Useful for Google Tag Manager)

isScrollable.js

// If using with GTM, anonymize the function name
function isScrollable() {
    function getDocumentHeight() {
        return Math.max(document.body.scrollHeight, document.body.offsetHeight,
            document.documentElement.clientHeight, document.documentElement.scrollHeight, document.documentElement.offsetHeight);
    }

    function getViewPortHeight() {
        return Math.max(document.documentElement.clientHeight, window.innerHeight || 0) * 2;
    }

    if (getViewPortHeight() < getDocumentHeight()) {
        return true;
    }
}