code: function googleOptimize({ experiment }) {
    if (process.server || !window.ga || !experiment || !experiment.experimentID) {
      return
    }
  
    const exp = experiment.experimentID + '.' + experiment.$variantIndexes.join('-')
  
    window.ga('set', 'exp', exp)
  }
docs: https://developers.google.com/optimize/devguides/experiments