old_contents: "use strict";
  /*global document*/
   var React = require('react');
  /**
   * Map containing all the mounted components.
   * @type {Object}
   */
   var mountedComponents = {};
  
  /**
   *  Render a react component in a DOM selector.
   * @param {object} component - A react component.
   * @param {string} selector  - A selector on a DOM node.
   * @param {object} options   - Options for the component rendering.
   * @return {undefined} - Return nothing.
   */
  module.exports = function(component, selector, options){
    options = options || {};
    //Unmount component if there is one mounted.
    if(mountedComponents[selector]){
      React.unmountComponentAtNode(document.getElementById(selector));
      console.log('component unmounted');
    }
    React.render(
      React.createElement(component, options.props, options.data),
      document.querySelector(selector)
    );
    //Save the fact that a comonent is mounted.
    mountedComponents[selector] = true;
    console.log('Mounted components : ', mountedComponents);
  };
  
new_contents: "use strict";
  /*global document*/
   var React = require('react');
  /**
   * Map containing all the mounted components.
   * @type {Object}
   */
   var mountedComponents = {};
  
  /**
   *  Render a react component in a DOM selector.
   * @param {object} component - A react component.
   * @param {string} selector  - A selector on a DOM node.
   * @param {object} options   - Options for the component rendering.
   * @return {undefined} - Return nothing.
   */
  module.exports = function(component, selector, options){
    options = options || {};
    //Unmount component if there is one mounted.
    if(mountedComponents[selector]){
      React.unmountComponentAtNode(document.querySelector(selector));
      console.log('component unmounted');
    }
    React.render(
      React.createElement(component, options.props, options.data),
      document.querySelector(selector)
    );
    //Save the fact that a comonent is mounted.
    mountedComponents[selector] = true;
    console.log('Mounted components : ', mountedComponents);
  };
  
subject: Fix selector bug in unmounting component.