var SetIntervalMixin = {

componentWillMount: function(){

this.intervals = [];

},

setInterval: function(){

this.intervals.push(setInterval.apply(null, arguments));

},

componentWillUnmount: function(){

this.intervals.forEach(clearInterval);

}

};

var TickTock = React.createClass({

mixins: [SetIntervalMixin],

getInitialState: function(){

return { seconds: 0 }

},

componentDidMount: function(){

this.setInterval(this.tick, 1000);

},

tick: function(){

this.setState({ seconds: this.state.seconds + 1 });

},

render: function(){

return (

<p>React has been running for {this.state.seconds} seconds.</p>

);

}

});

ReactDOM.render(

<TickTock />,

document.querySelector('.demo')

);