example.js

import React, { PropTypes } from 'react';
import LoadingIndicator from 'components/LoadingIndicator';

export const Test = () => (
  <LoadingIndicator isLoading>
    {() => (
      <div>
        This is only evaluated when isLoading===false
      </div>
    )}
  </LoadingIndicator>
);

LoadingIndicator.js

import 'loaders.css/loaders.css';
import './index.scss';
import React, { PropTypes } from 'react';

const LoadingIndicator = React.createClass({
    propTypes: {
        children: PropTypes.func.isRequired,
        isLoading: PropTypes.bool.isRequired 
    },
    render: function() {
        if(this.props.isLoading) {
            return <div className="loading-indicator-holder">
                <div className="loader-inner square-spin inner"><div></div></div>
            </div>;
        }

        return <div>{this.props.children()}</div>;
    }
});

export default LoadingIndicator;