hydrateStateWithLocalStorage()

App.js

hydrateStateWithLocalStorage() {
    // for all items in state
    for (let key in this.state) {
      // if the key exists in localStorage
      if (localStorage.hasOwnProperty(key)) {
        // get the key's value from localStorage
        let value = localStorage.getItem(key);

        // parse the localStorage string and setState
        try {
          value = JSON.parse(value);
          this.setState({ [key]: value });
        } catch (e) {
          // handle empty string
          this.setState({ [key]: value });
        }
      }
    }
  }