Function getInitializer

tensorboard/components/tf_storage/storage.ts:153–189

* Returns a function that can be used on a `value` declaration to a Polymer * property. It updates the `polymerProperty` when storage changes -- i.e., * when `useLocalStorage`, it listens to storage change from another tab and * when `useLocalStorage=false`, it listens to hashchange.

(key: string, options: StorageOptions<T>)

   * when `useLocalStorage=false`, it listens to hashchange.
   */
  function getInitializer(key: string, options: StorageOptions<T>): Function {
    const fullOptions = {
      defaultValue: options.defaultValue,
      polymerProperty: key,
      useLocalStorage: false,
      ...options,
    };
    return function () {
      const uriStorageName = getURIStorageName(this, key);
      // setComponentValue will be called every time the underlying storage
      // changes and is responsible for ensuring that new state will propagate
      // to the component with specified property. It is important that this
      // function does not re-assign needlessly, to avoid Polymer observer
      // churn.
      const setComponentValue = () => {
        const storedValue = get(uriStorageName, fullOptions);
        const currentValue = this[fullOptions.polymerProperty];
        if (!_.isEqual(storedValue, currentValue)) {
          this[fullOptions.polymerProperty] = storedValue;
        }
      };
      const addListener = fullOptions.useLocalStorage
        ? addStorageListener
        : addHashListener;
      // TODO(stephanwlee): When using fakeHash, it _should not_ listen to the
      //                    window.hashchange.
      const listenKey = addListener(() => setComponentValue());
      if (fullOptions.useLocalStorage) {
        storageListeners.push(listenKey);
      } else {
        hashListeners.push(listenKey);
      }
      // Set the value on the property.
      setComponentValue();
      return this[fullOptions.polymerProperty];
    };
  }
  function disposeBinding() {
    hashListeners.forEach((key) => removeHashListenerByKey(key));
    storageListeners.forEach((key) => removeStorageListenerByKey(key));