Edit in JSFiddle

var DOM = React.DOM
var App = React.createClass({
  getInitialState: function() {
    return {
      name: 'React',
        timestamp: 0
      }
    },
    handleClick: function() {
      this.setState({
        name: 'BOOOOOOOOOOOOOOOOM!!!!',
        timestamp: new Date().getTime() - this.props.start
      })
    },
    render: function() {
      return DOM.div(null, [
        DOM.h1(null, ['Welcome to ' + this.state.name + '!!']),
        DOM.div(null, [
          DOM.p(null, ["Watchout for what React you're using... it might not be real!"]),
          DOM.p(null, ["React is running for " + this.state.timestamp + "ms"])
        ]),
        DOM.a({ className: 'btn btn-default', onClick: this.handleClick.bind(this) }, ["Click me!!!"])
    ])
  }
})

var start = new Date().getTime()

React.render(
  React.createElement(App, { start: start }),
  document.getElementById('container')
)

<div id='container' class='container'></div>