gistfile1.js

React.createClass({

  getInitialState: function() {
    return { loading: true }
  },

  componentDidMount: function() {
    $.getJSON('/my/stuff', function (data) {
      this.setState({ stuff: data, loading: false })
    }.bind(this))
  },

  render: function() {
    if (this.state.loading) {
      <div class="loading" />;
    } else {
      // show the stuff
    }
  }
});