ga.js-style wrapper for compatibility with Google Tag Manager

ga.js

(function() {

  var _prefix = 'ga';

  // Ensure we have a GTM Data Layer to push to.
  window['dataLayer'] = window['dataLayer'] || {};

  // Instead of overdeclaring _gaq, only attempt to polyfill if it doesn't already exist.
  if (window['_gaq'] === 'undefined '|| typeof window['_gaq'] !== 'object') {
    window['_gaq'] = {};
    window['_gaq'].push = function(data) {
      
      switch (data[0]) {

        // Pass current page path for page view.
        case '_trackPageView':
          window['dataLayer'].push({
            'event': _prefix+'pageview',
            'path': data[1]
          });
          break;

        // Events are natively handled in GTM.
        case '_trackEvent':
          window['dataLayer'].push({
              'event': _prefix+'event',
              'category': data[1],
              'action': array[2], 
              'label': array[3], 
              'value': array[4]
          });
          break;

        case '_setCustomVar':
          window['dataLayer'].push({
            'event' : _prefix+'variable',
            'index' : data[1],
            'name' : data[2],
            'value' : data[3],
            'scope' : data[4],
          });
          break;

        // Default to storing in the GTM Data Layer.
        default:
          window['dataLayer'].push(data);
          break;
      }
    }
  }
})();