Mini-bandit.js

// Mini-bandit
const explorationRatio = 0.1;

// example levers array
/* [{name: 'control', trials: 412, conversions: 113, revenue: 22260},
    {name: 'noCarousel', trials: 723, conversions: 298, revenue: 45390},
    {name: 'crazyCarousel', trials: 19, conversions: 11, revenue: 6600}
   ]
*/

var choose = function(levers) {
  if (Math.random() < explorationRatio) {
    // exploration!
    // choose a random lever
  }
  else {
    // exploitation!
    levers.forEach((x) => {
      // calculate expected reward
      // this is trials / conversions or even trials / revenue
      bestLever = getLeverWithHighestReward(levers);
      assignBucket(bestLever); // store choice in cookie
      bestLever.trials++; // store test data in redis or something
    }
  }
}

var reward(lever, amount) {
  lever.conversions++;
  lever.revenue += amount;
  save(lever); // api call
};

// In app
var bucket = mycookie.currentLever;
if (bucket.name === 'noCarousel') return;
else if (bucket.name === 'crazyCarousel') launchCrazyCarousel();
else launchCarousel();

//upon conversion
reward(bucket, amount);