Add error to the state

RepoSearchPage.js

// src/containers/RepoSearchPage/page/RepoSearchPage.js

import React, { Component } from 'react';
import PropTypes from 'prop-types';
import { connect } from 'react-redux';
import { bindActionCreators } from 'redux';
import RepoResultsList from '../components/RepoResultsList/RepoResultsList';
import * as RepoSearchActions from '../actions/RepoSearchActions';

export class RepoSearchPage extends Component {
  constructor(props) {
    super(props);
  }

  componentWillMount() {
    this.props.actions.fetchRepos();
  }

  render() {
    // display error message when error string populated
    const { error, searchResults } = this.props;
    return (
      <div>
        <h1>Top Javascript Repos</h1>
        {error && <p>{error}</p>}
        <RepoResultsList repos={searchResults}/>
      </div>
    );
  }
}

RepoSearchPage.propTypes = {
  searchResults: PropTypes.array.isRequired,
  actions: PropTypes.object.isRequired,
  error: PropTypes.string,
};

RepoSearchPage.defaultProps = {
  error: '',
};

const mapStateToProps = state => ({
  searchResults: state.repoSearch.results,
  error: state.repoSearch.error,
});

const mapDispatchToProps = dispatch => ({
  actions: bindActionCreators(RepoSearchActions, dispatch),
});

export default connect(mapStateToProps, mapDispatchToProps)(RepoSearchPage);

RepoSearchReducer.js

// src/containers/RepoSearchPage/reducer/RepoSearchReducer.js

import { actionTypes } from '../RepoSearchConstants';

const initialState = {
  results: [],
  error: 'Oh dear'
};

export default (state = initialState, action) => {
  switch (action.type) {
    case actionTypes.UPDATE_RESULTS: {
      return { ...state, results: action.items };
    }
    default:
      return state;
  }
};