optimizely-ga-gtm-integration-with-event-and-custom-dimension.html

<script>
(function() {
    'use strict';
    var o = window.optimizely;
    window.optimizely = window.optimizely || [];
    window.dataLayer = window.dataLayer || [];

    if (o.activeExperiments && o.allExperiments) {
        for (var i = 0; i < o.activeExperiments.length; i++) {
            var experimentId = o.data.state.activeExperiments[i];
            var experimentName = experimentId;
            if (typeof o.data.experiments[experimentId] !== 'undefined') {
                experimentName = o.data.experiments[experimentId].name;
            }
            var variationName = o.data.state.variationNamesMap[experimentId];

            dataLayer.push({
                'event': 'optimizelyEvent',
                'eventCategory': 'Optimizely',
                'eventAction': experimentName,
                'eventLabel': variationName
            });
        }
    }
})();
</script>