Replace AngularJS component by a React component using redux

July 28, 2018

Redux is a state management library for Javascript applications. I use it in big React or AngularJS applications. In order to migrate efficiently from AngularJS to React, I transformed my AngularJS 1.6 components to smaller components using redux.

I can create a component and connect state to them. Like this I separate my redux store from my components. All actions and state values from redux are decoupled from my component and passed as props to it.

One strategy for your AngularJS to React migration is to start one component per component. In this blog post I will show you how to replace an AngularJS component using redux by a React component.

Typical AngularJS component binded with redux

Example of a Menu component using user from state and logout action

Menu
├── Menu.js
├── MenuController.js
└── Menu.html

Menu.html

<ul class="Menu">
    <li>
        <a href="/settings"></a>
    </li>
    <li>
        <button type="button" class="btn btn-link" ng-click="$ctrl.logout()">
            logout
        </button>
    </li>
</ul>

MenuController.js

import { logout } from "auth/authActions";

class MenuController {
  constructor($scope, $ngRedux) {
    this.$ngRedux = $ngRedux;
    let unsubscribe = $ngRedux.connect(this.mapStateToProps, this.mapDispatchToProps)(this);
    $scope.$on("$destroy", unsubscribe);
  }
  
  mapStateToProps(state) {
    return {
      user: state.user
    };
  }

  mapDispatchToProps(dispatch) {
    return {
      logout: () => dispatch(logout())
    };
  }
}

MenuController.$inject = ["$scope", "$ngRedux"];

This is the recommended way to connect ng-redux the Angular binding for redux in an AngularJS component.

Menu.js

import template from "./Menu.html";
import controller from "./MenuController";

export default {
  template,
  controller
};

You can import your Angular Component into your App

import Menu from "./Menu";

angular
  .module("app", [ngRedux])
  .component("myMenu", Menu);

React Menu component

We can now create a React component with the same behaviour

MenuReact.js

import React, { Component } from "react";
import { connect } from "react-redux";
import { logout } from "auth/authActions";

export class Menu extends Component {
  render() {
    const { user, logout } = this.props;
    return (
      <ul className="Menu">
        <li>
          <a href="/settings">{user.name}</a>
        </li>
        <li>
          <button
            type="button"
            className="btn btn-link"
            onClick={() => logout()}
          >
            logout
          </button>
        </li>
      </ul>
    );
  }
}

function mapStateToProps(state) {
  return {
    user: state.user
  };
}

function mapDispatchToProps(dispatch) {
  return {
    logout: () => dispatch(logout())
  };
}

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

You can see the difference between the HTML and the JSX. class => className, ng-click => onClick, "$ctrl.logout()" => {() => logout()}

You can see the mapStateToProps and mapDispatchToProps equivalence. Redux is framework agnostic. It’s interesting to note that the more work you do in redux, the easier the migration will be.

Connect problem

In a regular React application, we integrate our containers to the store, using the method connect from react-redux. It works because all our components are under the Provider component.

ReactDOM.render(
  <Provider store={store}>
    <Menu />
  </Provider>,
  document.getElementById('root')
)

In a typical AngularJS redux application we don’t have the same mechanism. We cannot take our React component and replace it as this in our AngularJS application.

Every component is a root component. So we should use a High Order Component (HOC) to insert the Provider as a wrapper when necessary.

You can use redux-connect-standalone HOC:

npm install redux-connect-standalone

store.js

import createConnect from 'redux-connect-standalone';

export const rootReducer = combineReducers({...});
const store = createStore(rootReducer, applyMiddleware(thunk));
export default store;

export const connect = createConnect(store);

You can now replace import { connect } from "react-redux"; by import { connect } from "../store"; in your MenuReact.js file.

react2angular

We can now replace our AngularJS component by our new fresh React one. To do so, we are going to use react2angular and prop-types npm modules.

npm install react2angular prop-types

prop-types is used to add props info to our component to avoid specifying them in react2angular.

Just add the following code into MenuReact.js

Menu.propTypes = {
  user: PropTypes.object.isRequired,
  logout: PropTypes.func.isRequired
};

We can now replace our AngularJS component by our React one

import Menu from "./Menu/MenuReact";
import { react2angular } from "react2angular";

angular
  .module("app", [ngRedux])
  .component("myMenu", react2angular(Menu))

We will discuss in another post the good strategy to facilitate the migration.

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