Integration with Single Page Application (React)
To provide the page hosting the React SPA, you will need to implement a custom module. This module would also contains all the JavaScript code of your application. If that's the only usage of React in your site, I suggest bundling everything in the module to make it easier.

I assume you should be able to retrieve the user authentication token and any other needed info in Drupal. You can then pass it to your application using drupal_add_js() (or #attach in a render array). Your application can then retrieve it with Drupal.settings

/**
 * Implements hook_menu().
 */
function MODULE_menu() {
  return [
    'admin/APPLICATION/PATH' =&gt; [
      'title' =&gt; 'Awesome React Application',
      'page callback' =&gt; 'MODULE_application_page',
      'access arguments' =&gt; 'access administration pages'
    ]
  ];
}

/**
 * Page callback for the application page.
 *
 * @return The page as a render array with #attached JS and CSS code.
 */
function MODULE_application_page() {
  global $user;
  $app_data = clone $user;
  unset($app_data-&gt;pass);
  $app_data-&gt;token = MODULE_get_user_token();
  $base_assets_path = drupal_get_path('module', 'MODULE');
  return [
    '#type' =&gt; 'markup',
    '#markup' =&gt; '&lt;div id="MODULE-app-container"&gt;&lt;/div&gt;',
    '#attached' =&gt; [
      'css' =&gt; ["$base_assets_path/css/app.css" =&gt; ['preprocess' =&gt; FALSE]],
      'js' =&gt; [
        "$base_assets_path/js/app.js" =&gt; ['preprocess' =&gt; FALSE],
        [
          'type' =&gt; 'settings',
          'data' =&gt; ['MODULE' =&gt; $app_data]
        ]
      ],
    ]
  ];
}