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HTML

              
                <div id="app"></div>
              
            
!

CSS

              
                html, body {
  height: 100%;
}

body {
  display: flex;
  justify-content: center;
  align-items: center;
  font-family: Helvetica Neue;
}
              
            
!

JS

              
                class MovieItem extends React.Component {

  componentDidMount() {
    // When the component is mounted, add your DOM listener to the "nv" elem.
    // (The "nv" elem is assigned in the render function.)
    this.nv.addEventListener("nv-enter", this.handleNvEnter);
    
    // Testing
    setInterval(() => this.nv.dispatchEvent(new CustomEvent("nv-enter", { detail: new Date() })), 1000);
  }

  componentWillUnmount() {
    // Make sure to remove the DOM listener when the component is unmounted.
    this.nv.removeEventListener("nv-enter", this.handleNvEnter);
  }

  // Use a class arrow function (ES7) for the handler. In ES6 you could bind()
  // a handler in the constructor.
  handleNvEnter = (event) => {
    console.log("Nv Enter:", event);
  };

  render() {
    // Here we render a single <div> and toggle the "aria-nv-el-current" attribute
    // using the attribute spread operator. This way only a single <div>
    // is ever mounted and we don't have to worry about adding/removing
    // a DOM listener every time the current index changes. The attrs 
    // are "spread" onto the <div> in the render function: {...attrs}
    const attrs = this.props.index === 0 ? {"aria-nv-el-current": true} : {};

    // Finally, render the div using a "ref" callback which assigns the mounted 
    // elem to a class property "nv" used to add the DOM listener to.
    return (
      <div ref={elem => this.nv = elem} aria-nv-el {...attrs} className="menu_item nv-default">
        Check out the log console
      </div>
    );
  }

}

ReactDOM.render(<MovieItem />, document.getElementById("app"));
              
            
!
999px

Console