Subscribe to changes of part of a redux tree

redux-watch.js

import get from "lodash.get";
import isEqual from "lodash.isequal";

/**
 * Subscribe to changes of part of a redux tree
 *
 * @example
 *   watch(Store, "dataset.currentId", id => {
 *     console.log(id);
 *   });
 * @param {Redux.Store} Store - Redux store created with createStore()
 * @param {string} path - The path of the property to watch
 * @param {function} cb - Callback that is executed on change with (cur, prev)
 * @returns {void}
 */
const watch = (Store, path, cb) => {
  let currentState;
  Store.subscribe(() => {
    let prevState = currentState;
    currentState = get(Store.getState(), path);
    if (!isEqual(prevState, currentState)) {
      cb(currentState, prevState);
    }
  });
};

export default watch;