React – animate mount and unmount of a single component

Question

This is a bit lengthy but I’ve used all the native events and methods to achieve this animation. No ReactCSSTransitionGroup, ReactTransitionGroup and etc.

Things I’ve used

React lifecycle methods
onTransitionEnd event

How this works

Mount the element based on the mount prop passed(mounted) and with default style(opacity: 0)
After mount or update, use componentDidMount (componentWillReceiveProps for further updates)to change the style (opacity: 1) with a timeout(to make it async).
During unmount, pass a prop to the component to identify unmount, change the style again(opacity: 0), onTransitionEnd, remove unmount the element from the DOM.

Continue the cycle.

Go through the code, you’ll understand. If any clarification is needed, please leave a comment.

Hope this helps.

class App extends React.Component{
  constructor(props) {
    super(props)
    this.transitionEnd = this.transitionEnd.bind(this)
    this.mountStyle = this.mountStyle.bind(this)
    this.unMountStyle = this.unMountStyle.bind(this)
    this.state ={ //base css
      show: true,
      style :{
        fontSize: 60,
        opacity: 0,
        transition: 'all 2s ease',
      }
    }
  }
  
  componentWillReceiveProps(newProps) { // check for the mounted props
    if(!newProps.mounted)
      return this.unMountStyle() // call outro animation when mounted prop is false
    this.setState({ // remount the node when the mounted prop is true
      show: true
    })
    setTimeout(this.mountStyle, 10) // call the into animation
  }
  
  unMountStyle() { // css for unmount animation
    this.setState({
      style: {
        fontSize: 60,
        opacity: 0,
        transition: 'all 1s ease',
      }
    })
  }
  
  mountStyle() { // css for mount animation
    this.setState({
      style: {
        fontSize: 60,
        opacity: 1,
        transition: 'all 1s ease',
      }
    })
  }
  
  componentDidMount(){
    setTimeout(this.mountStyle, 10) // call the into animation
  }
  
  transitionEnd(){
    if(!this.props.mounted){ // remove the node on transition end when the mounted prop is false
      this.setState({
        show: false
      })
    }
  }
  
  render() {
    return this.state.show && <h1 style={this.state.style} onTransitionEnd={this.transitionEnd}>Hello</h1> 
  }
}

class Parent extends React.Component{
  constructor(props){
    super(props)
    this.buttonClick = this.buttonClick.bind(this)
    this.state = {
      showChild: true,
    }
  }
  buttonClick(){
    this.setState({
      showChild: !this.state.showChild
    })
  }
  render(){
    return <div>
        <App onTransitionEnd={this.transitionEnd} mounted={this.state.showChild}/>
        <button onClick={this.buttonClick}>{this.state.showChild ? 'Unmount': 'Mount'}</button>
      </div>
  }
}

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

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.3.2/react-with-addons.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="app"></div>

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