simple-widget.js

var Hello = React.createClass({
  getInitialState: function(){
    return {
    }
  },
  updateName: function(event){
  	this.setState({
      name: event.target.value
    })
  },
  render: function() {
    return (
      <div>
        <input type="text" 
          onChange={this.updateName}/>
        <strong>Hello</strong> {this.state.name}
      </div>
    )
  }
});

ReactDOM.render(
  <div>
  	<Hello name="World" />
  </div>,
  document.getElementById('container')
);