 route.</p>
<p>The <code>error</code> and <code>loading</code> substates exist as a part of each route, so they
should not be added to your <code>router.js</code> file. To utilize a substate, the route, controller,
and template may be optionally defined as desired.</p>
<h2 id="toc_loading-substates"><code>loading</code> substates <a href="#toc_loading-substates"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512">
        <path d="M326.61 185.4c59.75 59.8 58.93 155.69.36 214.58-.1.12-.24.25-.36.37