event listener in react
var Box = React.createClass({
  getInitialState: function() {
    return {windowWidth: window.innerWidth};
  },
  handleResize: function(e) {
    this.setState({windowWidth: window.innerWidth});
  },
  componentDidMount: function() {
    window.addEventListener('resize', this.handleResize);
  },
  componentWillUnmount: function() {
    window.removeEventListener('resize', this.handleResize);
  },
  render: function() {
    return <div>Current window width: {this.state.windowWidth}</div>;
  }
});
ReactDOM.render(<Box />, mountNode);
