talk/plugins/talk-plugin-remember-sort/client/index.js

import {setSort} from 'plugin-api/beta/client/actions/stream';
import {sortOrderSelector, sortBySelector} from 'plugin-api/beta/client/selectors/stream';

const STORAGE_PATH = 'talkPluginRememberSort';

export default {
  init: async ({store, pymStorage, introspection}) => {

    // TODO: workaround as this plugin is included in any target and
    // embeds (e.g. admin), but should only be included inside the stream.

    // Detect if we are currently running inside the stream.
    if (!store.getState().stream) {
      return;
    }

    // We use pymStorage instead to persist the data directly on the parent page,
    // in order to mitigate strict cross domain security settings.

    let sort = JSON.parse(await pymStorage.getItem(STORAGE_PATH));
    if (
      sort &&
      introspection.isValidEnumValue('SORT_ORDER', sort.sortOrder) &&
      introspection.isValidEnumValue('SORT_COMMENTS_BY', sort.sortBy)
    ) {
      store.dispatch(setSort(sort));
    }
    store.subscribe(() => {
      const state = store.getState();
      const sortOrder = sortOrderSelector(state);
      const sortBy = sortBySelector(state);

      // Save sorting choice to storage if it has changed.
      if (!sort || sort.sortOrder !== sortOrder || sort.sortBy !== sortBy) {
        sort = {sortOrder, sortBy};
        pymStorage.setItem(STORAGE_PATH, JSON.stringify(sort));
      }
    });
  }
};