Carousel: use combined selector and drop variable used once

Author: GeoSot

js/src/carousel.js

@@ -56,8 +56,8 @@ const CLASS_NAME_NEXT = 'carousel-item-next'
 const CLASS_NAME_PREV = 'carousel-item-prev'
 
 const SELECTOR_ACTIVE = '.active'
-const SELECTOR_ACTIVE_ITEM = '.active.carousel-item'
 const SELECTOR_ITEM = '.carousel-item'
+const SELECTOR_ACTIVE_ITEM = SELECTOR_ACTIVE + SELECTOR_ITEM
 const SELECTOR_ITEM_IMG = '.carousel-item img'
 const SELECTOR_NEXT_PREV = '.carousel-item-next, .carousel-item-prev'
 const SELECTOR_INDICATORS = '.carousel-indicators'