react: fade-in/slide-in animation when render component

Question

I'm new in React. I have made a small app with a button and a list of image urls. When button is clicked, an image url is added to the list. I render the list of image urls with standard .map function.

I would like to make a fast ui animation effect when the image is displayed: a combination of fade-in and slide-in from left. I tried Velocity.js and found the velocity-react wrapper. But I can not understand how to use it. The same goes for the 'standard' velocity-animate library.

What is best? velocity-react, velocity-animate or something else? And how do I do it?

JSX

<div className="row">
  {
    this.state.images.map( (image, index) => { return this.renderThumb(image, index); } )
  }
</div>

renderThumb function

renderThumb(image, index) {
  return (
    <div ref="tweetImage" key={`image-${index}`} className="col-xs-3 tweetImage">
      <img className="img-thumbnail" src={image} alt="my pic"/>
    </div>
  );
}

velocity-react

I tried to wrap <img> animation opacity from 0 to 1 like this (copied from docs):

<VelocityComponent animation={{ opacity: 1 }} duration={ 500 }>
  <img className="img-thumbnail" src={image} alt="my pic"/>
</VelocityComponent

I keep getting this error:

Warning: React.createElement: type is invalid -- expected a string (for built-in components) or a class/function (for composite components) but got: object

---

No luck with ReactCSSTransitionGroup either (like suggestions below). Images are shown but without animation:

renderThumb(image, index) {
  return (
    <div ref="tweetImage" key={`image-${index}`} className="col-xs-3">
      <ReactCSSTransitionGroup
        transitionName="example">
          <img className="img-thumbnail" src={image} alt="Ole Frank Jensen"/>
      </ReactCSSTransitionGroup>
    </div>
  );
}

---

SOLVED:

I moved <ReactCSSTransitionGroup transitionName="example"> outside of the fading component and voilá :-)

render()

<div className="row">
  <ReactCSSTransitionGroup transitionName="example">
    {
      this.state.images.map( (image, index) => { return this.renderThumb(image, index); } )
    }
  </ReactCSSTransitionGroup>
</div>

renderThumb()

renderThumb(image, index) {
  return (
    <div key={`image-${index}`} className="col-xs-3">
      <img className="img-thumbnail" src={image} alt="Ole Frank Jensen"/>
    </div>
  );
}

Answer 1

You can use the CSSTransitionGroup provided by react.

https://facebook.github.io/react/docs/animation.html

a simple todo exammple from the docs

class TodoList extends React.Component {
  constructor(props) {
    super(props);
    this.state = {items: ['hello', 'world', 'click', 'me']};
    this.handleAdd = this.handleAdd.bind(this);
  }

  handleAdd() {
    const newItems = this.state.items.concat([
      prompt('Enter some text')
    ]);
    this.setState({items: newItems});
  }

  handleRemove(i) {
    let newItems = this.state.items.slice();
    newItems.splice(i, 1);
    this.setState({items: newItems});
  }

  render() {
    const items = this.state.items.map((item, i) => (
      <div key={item} onClick={() => this.handleRemove(i)}>
        {item}
      </div>
    ));

    return (
      <div>
        <button onClick={this.handleAdd}>Add Item</button>
        <ReactCSSTransitionGroup
          transitionName="example"
          transitionEnterTimeout={500}
          transitionLeaveTimeout={300}>
          {items}
        </ReactCSSTransitionGroup>
      </div>
    );
  }
}