React Base Fiddle (JSX)

Starting point for creating JSFiddles with React. This uses React with Addons.

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/babel-core/5.8.24/browser.js"></script>
<script src="https://fb.me/react-with-addons-15.0.1.js"></script>
<script src="https://fb.me/react-dom-15.0.1.js"></script>
<script src="https://facebook.github.io/react/js/jsfiddle-integration-babel.js"></script>

<div id="container">
    <!-- This element's contents will be replaced with your component. -->
</div>

JavaScript 1.7

var Box = React.createClass({
        render: function() {
          return (
            <div>Box</div>
          );
        }
      });
      
      var CommentBox = React.createClass({
        getInitialState: function() {
          return {boxes: [<Box key="first" />], maxBoxes: 5};
        },
        
        heavyLoadRender: function() {
          setTimeout(() => {
            if (this.state.boxes.length < 50000) {
              this.setState({ 
                boxes: this.state.boxes.concat(<Box key={this.state.boxes.length} />)
              })
              this.heavyLoadRender()
            }
          })
        },
        
        render: function() {
          return (
            <div>
             <button onClick={this.heavyLoadRender}>Start</button>
              {this.state.boxes}
            </div>
          );
        }
      });
      
      ReactDOM.render(
        <CommentBox />,
        document.getElementById('container')
      );