React-Transition-Group CSSTransition Example (NodeJS)

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1- The objectives of this lesson

The  react-transition-group library provides you with components so that you create animation effects in the React application. The following post introduces in details this library, its components, APIs, etc.
In this lesson, I will guide you to create  React applications on the  NodeJS environment, using the  <CSSTransition> component provided by the  react-transition-group ​​​​​​​library.
Note: The  <CSSTransition> component is a private case helping work with  CSS Transition more easily. In general case, you should work with the  <Transition> component.

2- Create a project and install a library

Create a  React project with the  csstransition-app name by performing the following commands:
# Install 'create-react-app' tool (If it has never been installed)

npm install -g create-react-app

# Create project with 'create-react-app' tool:

create-react-app csstransition-app
Install the  react-transition-group ​​​​​​​library:
# CD to your project

cd csstransition-app

# Install 'react-transition-group':

npm install react-transition-group --save
Run your application:
# Run app:

npm start

3- Simple CSSTransition example

OK, below is the preview of this example.
When the value of props: 'in' changes from  false to  true, <CSSTransition> will change to the  'entering' status and keeps in this status in   'timeout' miliseconds, before changing to the  'entered' status. During such process, the  CSS classes wil apply to the child element of the  <CSSTransition>, like the following illustration:
When the value of  props: 'in' changes from  true to  false. The <CSSTransition> will change to the  'exiting' status and keeps in this status in   'timeout' miliseconds, before changing to the  'exited' status. During such process, the  CSS classes wil apply to the child element of the  <CSSTransition>, like the following illustration:
OK, Come back to the above project. Delete all the contents of the  App.js & App.css files:
.example-enter {
  opacity: 0.2;
  transition: opacity 300ms ease-in;
  background:  #f9e79f;

.example-enter .example-enter-active {
  opacity: 1;
  background:  #eafaf1 ;

.example-enter-done {
  opacity: 1;
  background:  #eafaf1 ;

.example-exit {
  opacity: 1;
  transition: opacity 900ms ease-in;
  background:  #fdebd0 ;

.example-exit .example-exit-active {
  opacity: 0.5;
  background:  white ;

.example-exit-done {
  opacity: 1;
  background:  white;

.my-div {
  border: 1px solid blue;
  width: 350px;
  height: 150px;
  padding: 5px;

.my-message {
   font-style: italic;
   color: blue;

.my-highlight  {
  color: red;
import React, { Component } from 'react';
import logo from './logo.svg';
import './App.css';

import { TransitionGroup, CSSTransition } from "react-transition-group";

class App extends React.Component  {

    render()  {
      return (

class MyDiv extends React.Component {
  constructor(props) {
    this.state = {
      stateOfIn: false,
      message : ""

  // Begin Enter: Do anything!
  onEnterHandler()  {
     this.setState({message: 'Begin Enter...'});

  onEnteredHandler ()  {
     this.setState({message: 'OK Entered!'});

  onEnteringHandler() {
     this.setState({message: 'Entering... (Wait timeout!)'});

  // Begin Exit: Do anything!
  onExitHandler() {
     this.setState({message: 'Begin Exit...'});

  onExitingHandler() {
     this.setState({message: 'Exiting... (Wait timeout!)'});

  onExitedHandler() {
     this.setState({message: 'OK Exited!'});

  render()  {

    return (


              onEnter = {() =>  this.onEnterHandler()}
              onEntering = {() =>  this.onEnteringHandler()}
              onEntered={() =>  this.onEnteredHandler()}

              onExit={() =>  this.onExitHandler()}
              onExiting={() =>  this.onExitingHandler()}
              onExited={() =>  this.onExitedHandler()}
              <div className ="my-div">
                 <b>{"\u2728"} Click the buttons and see the effects:</b>
                    <li className ="my-highlight">Now 'in' = {String(this.state.stateOfIn)}</li>
                    <li>  false --&gt; true (Enter)</li>
                    <li>  true  --&gt; false (Exit)</li>
                 <div className="my-message">{this.state.message}</div>

            <h3>&lt;CSSTransition in={'{this.state.stateOfIn}'} &gt;</h3>

            <button onClick={() => {this.setState({ stateOfIn: true });}}>Set stateOfIn = true</button>
            <button onClick={() => {this.setState({ stateOfIn: false });}}>Set stateOfIn = false</button>

export default App;
It is not necessary to change the contents of the  index.js & index.html files:
import React from 'react';
import ReactDOM from 'react-dom';
import './index.css';
import App from './App';
import * as serviceWorker from './serviceWorker';

ReactDOM.render(<App />, document.getElementById('root'));

// If you want your app to work offline and load faster, you can change
// unregister() to register() below. Note this comes with some pitfalls.
// Learn more about service workers:
<!DOCTYPE html>
<html lang="en">
    <meta charset="utf-8">
    <link rel="shortcut icon" href="%PUBLIC_URL%/favicon.ico">
    <meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">
    <meta name="theme-color" content="#000000">
    <link rel="manifest" href="%PUBLIC_URL%/manifest.json">
    <title>React CssTransition</title>
      You need to enable JavaScript to run this app.
    <div id="root"></div>

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