set d to true for console debugging

optimizely-gtm-custom-integration.js

(function() {
    var d = false;
    window.optimizely = window.optimizely || [];
    var o = window.optimizely;

    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];

            if (d) console.info('You are in experiment "' + experimentName + '" and in variation "' + variationName + '".');

            window.dataLayer = window.dataLayer || [];
            dataLayer.push({
                'event': 'optimizelyEvent',
                'eventCategory': 'Optimizely',
                'eventAction': experimentName,
                'eventLabel': variationName
            });
            if (d) console.log('Experiment infomation pushed to dataLayer.');

        }
    }

})();