Why I can't found the loader element from parent element? : here is the full code: https://codepen.io/dotku/pen/gyVZqj?editors=1011

```html
<div id="carousel">
  <span class="loader">Loading...</span>
</div>
```

```js
  if (!containerElement) {
    console.log('Carousel element is required.')
    return;
  } else {
    console.log(
      'Carousel element is found',
      document.querySelector(`#${containerID}`)
    );
  }
```

I have a checking statement, but the document.querySelector won't return the loader, why?

