function pushButtonGtm(eventLabel) {
    dataLayer.push({ 'shortcodeType': 'button', 'event': 'GA Button Shortcode Event', 'eventLabel': eventLabel });
}

var _btn = document.querySelectorAll("[data-gtm]");
var forEachHelper = function (array, callback, scope) {
    for (var i = 0; i < array.length; i++) {
        callback.call(scope, i, array[i]); // passes back stuff we need
    }
};
forEachHelper(_btn, function (index, value) {
    value.addEventListener("click", function (e) {
        var gtmData = e.srcElement.dataset.gtm;
        var isShortcode = e.srcElement.dataset.shortcode;
        if (isShortcode !== undefined && isShortcode !== null) {
            if (gtmData !== null || gtmData !== undefined) {
                pushButtonGtm(gtmData);
            }
        }
    });
});