PR comment

packages/gallery/src/components/gallery/proGallery/slideshowView.js

@@ -435,21 +435,17 @@ class SlideshowView extends React.Component {
   };
 
   getFirstIdx(itemIdx) {
-    const activeItem = this.props.galleryStructure.galleryItems[itemIdx];
-    const activeItemId = activeItem.itemId;
-    const firstItemInstance = this.props.galleryStructure.galleryItems.find((item) => item.itemId === activeItemId);
-    return firstItemInstance.idx;
+    const { galleryItems } = this.props.galleryStructure;
+    const activeItemId = galleryItems[itemIdx].itemId;
+    return galleryItems.find((item) => item.itemId === activeItemId).idx;
   }
 
   scrollToThumbnail(itemIdx, scrollDuration) {
     //not to confuse with this.props.actions.scrollToItem. this is used to replace it only for thumbnail items
 
     this.props.actions.eventsListener(GALLERY_CONSTS.events.THUMBNAIL_CLICKED, this.props);
-    const activeItemFirstIdx = this.getFirstIdx(this.state.activeIndex);
-    const firstTargetItemIdx = this.getFirstIdx(itemIdx);
-    const distance = firstTargetItemIdx - activeItemFirstIdx;
-    const targetIdx = this.state.activeIndex + distance;
-
+    const activeIdx = this.state.activeIndex;
+    const targetIdx = activeIdx + (this.getFirstIdx(itemIdx) - this.getFirstIdx(activeIdx));
     this.scrollToIndex({ itemIdx: targetIdx, scrollDuration });
   }