REACT JS ANIMATIONS

In this chapter, we will learn how to animate elements using React.

Step 1 - Install React CSS Transitions Group

This is React add-on used for creating basic CSS transitions and animations. We will install it from the command promptwindow −

C:\Users\username\Desktop\reactApp>npm install react-addons-css-transition-group

Step 2 - Add a CSS file

Let's create a new folder css and file style.css inside. To be able to use it in the app, we need to link it to the head element in index.html.

<link rel = "stylesheet" type = "text/css" href = "css/style.css">

Step 3 - Appear Animation

We will create a basic React component. The ReactCSSTransitionGroup element will be used as a wrapper of the component we want to animate. It will use transitionAppear and transitionAppearTimeout, while transitionEnter and transitionLeave are false.

App.jsx

import React from 'react';
var ReactCSSTransitionGroup = require('react-addons-css-transition-group');

class App extends React.Component {
   render() {
      return (
         <div>
            <ReactCSSTransitionGroup transitionName = "example"
               transitionAppear = {true} transitionAppearTimeout = {500}
               transitionEnter = {false} transitionLeave = {false}>
     
               <h1>My Element...</h1>
            </ReactCSSTransitionGroup>
         </div>      
      );
   }
}
export default App;

main.js

import React from 'react'
import ReactDOM from 'react-dom';
import App from './App.jsx';

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

The CSS animation is very simple.

css/style.css

.example-appear {
   opacity: 0.01;
}
.example-appear.example-appear-active {
   opacity: 1;
   transition: opacity 500ms ease-in;
}

Once we start the app, the element will fade in.

Step 4 - Enter and Leave Animations

Enter and leave animations can be used when we want to add or remove elements from the list.

App.jsx

import React from 'react';
var ReactCSSTransitionGroup = require('react-addons-css-transition-group');

class App extends React.Component {
   constructor(props) {
      super(props);
  
      this.state = {
         items: ['Item 1...', 'Item 2...', 'Item 3...', 'Item 4...']
      }
      this.handleAdd = this.handleAdd.bind(this);
   };
   handleAdd() {
      var newItems = this.state.items.concat([prompt('Create New Item')]);
      this.setState({items: newItems});
   }
   handleRemove(i) {
      var newItems = this.state.items.slice();
      newItems.splice(i, 1);
      this.setState({items: newItems});
   }
   render() {
      var items = this.state.items.map(function(item, i) {
         return (
            <div key = {item} onClick = {this.handleRemove.bind(this, i)}>
               {item}
            </div>
         );
      }.bind(this));
      
      return (
         <div>      
            <button onClick = {this.handleAdd}>Add Item</button>
    
            <ReactCSSTransitionGroup transitionName = "example" 
               transitionEnterTimeout = {500} transitionLeaveTimeout = {500}>
               {items}
            </ReactCSSTransitionGroup>
         </div>
      );
   }
}
export default App;

main.js

import React from 'react'
import ReactDOM from 'react-dom';
import App from './App.jsx';

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

css/style.css

.example-enter {
   opacity: 0.01;
}
.example-enter.example-enter-active {
   opacity: 1;
   transition: opacity 500ms ease-in;
}
.example-leave {
   opacity: 1;
}
.example-leave.example-leave-active {
   opacity: 0.01;
   transition: opacity 500ms ease-in;
}

When we start the app and click the Add Item button, the prompt will appear.

Once we enter the name and press OK, the new element will fade in.

Now we can delete some of the items (Item 3...) by clicking it. This item will fade out from the list.

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