How to make React animation on Hover?

Question

I need to move menu item underline like in this example.

With jQuery I would do it simply getting left position and width of a menu item. And then perform stop.animation on hover.

I'm trying to do such animation with React. But I can't figure out how to. After google research I found the popular react-motion library for animation. But I can't find the way how to trigger animation on hover.

My task is move blue underline on div hover. Please help me to find the solution.

Answer 1

You can do this using a css transition and an absolutely positioned stripe for the under line. Then update the left property of the stripe when the element is hovered.

class App extends React.Component {
  constructor() {
    super()
    this.state = {
      left: 0,
    }
  }
  
  handleMouseEnter = (e) => {
    this.setState({
      left: e.target.getBoundingClientRect().x - 8,
    });
  }

  render() {
    return (
      <div className="App">
        <div className="box" onMouseEnter={this.handleMouseEnter} />
        <div className="box" onMouseEnter={this.handleMouseEnter}  />
        <div className="box" onMouseEnter={this.handleMouseEnter}  />
        <div className="box" onMouseEnter={this.handleMouseEnter}  />
        <div className="stripe" style={{ left: this.state.left }}/>
      </div>
    );
  }
}

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

.App {
  width: 900px;
  overflow: hidden;
  position: relative;
  padding-bottom: 20px;
}
.box {
  width: 200px;
  height: 200px;
  background: #eee;
  border: 1px solid #333;
  float: left;
  margin-right: 10px;
}
.stripe {
  width: 200px;
  height: 10px;
  background: blue;
  position: absolute;
  bottom: 0;
  transition: left 0.3s;
}

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

Here is an example on codepen