Pay attention to which variable you're using!

index.js

// Wrong!!!
self.addEventListener('activate', function(event) {
  var cacheWhitelist = ['v2'];

  event.waitUntil(
    // TODO: remove the old cache
    caches.keys().then(function(keyList) {
      return Promise.all(
        keyList.map(function(key) {
          if (cacheWhitelist.indexOf(key) === -1) {
            console.log(key);
            return caches.delete(key);
          }
        })
      );
    })
  );
});

// Right!
self.addEventListener('activate', function(event) {
  var cacheWhitelist = ['v2'];

  event.waitUntil(
    // TODO: remove the old cache
    caches.keys().then(function(keyList) {
      return Promise.all(
        keyList.map(function(key) {
          if (key.indexOf(cacheWhitelist) === -1) {
            return caches.delete(key);
          }
        })
      );
    })
  );
});