var gaTracker = (function(dLayer) {

    // Push the object to the dataLayer
    // Parameters:
    // eventName, category, action, label, Type String
    // value Type Number (int)
    var pushEventToDataLayer = function(eventName, category, action, label, value) {
        dLayer.push({
            "event": eventName, // on GTM this would be the event that triggers the tag.
            "category": category,
            "action": action,
            "label": label,
            "value": value
        });
    };

    var isUniversalAnalytics = function(ga) {
        return typeof ga !== "undefined" && typeof ga.getAll === 'function' ? true : false;
    }

    var isClassicAnalytics = function(_gat) {
        return typeof _gat !== "undefined" && typeof _gat._getTrackers === 'function' ? true : false;
    }

    // decorate target URL for cross domain tracker.
    var decorateLink = function(url) {
        var trackers, linker;

        if (isUniversalAnalytics(ga)) {
            trackers = ga.getAll();
            if (trackers.length) {
                linker = new window.gaplugins.Linker(trackers[0]);
                url = linker.decorate(url);
            }
        }

        if (isClassicAnalytics(_gat)) {
            trackers = _gat._getTrackers();
            if (trackers.length) {
                url = trackers[0]._getLinkerUrl(url);
            }
        }

        return url;
    };

    return {
        "event": pushEventToDataLayer,
        "decorateLink": decorateLink
    };

})(dataLayer);

var gaTracker = (function(dLayer) {

    // Push the object to the dataLayer
    // Parameters:
    // eventName, category, action, label, Type String
    // value Type Number (int)
    var pushEventToDataLayer = function(eventName, category, action, label, value) {
        dLayer.push({
            "event": eventName, // on GTM this would be the event that triggers the tag.
            "category": category,
            "action": action,
            "label": label,
            "value": value
        });
    };

    var isUniversalAnalytics = function(ga) {
        return typeof ga !== "undefined" && typeof ga.getAll === 'function' ? true : false;
    };

    var isClassicAnalytics = function(_gat) {
        return typeof _gat !== "undefined" && typeof _gat._getTrackers === 'function' ? true : false;
    };

    // decorate target URL for cross domain tracker.
    var decorateLink = function(url) {
        var trackers, linker;

        if (isUniversalAnalytics(ga)) {
            trackers = ga.getAll();
            if (trackers.length) {
                linker = new window.gaplugins.Linker(trackers[0]);
                url = linker.decorate(url);
            }
        } else if (isClassicAnalytics(_gat)) {
            trackers = _gat._getTrackers();
            if (trackers.length) {
                url = trackers[0]._getLinkerUrl(url);
            }
        }

        return url;
    };

    return {
        "event": pushEventToDataLayer,
        "decorateLink": decorateLink
    };

})(dataLayer);

Add missing semi-colons and if/else that statement