prevPage handle

* go back to previous chapter on page 0 when prevPage is triggered

webUI/react/src/screens/Reader.tsx

@@ -139,6 +139,7 @@ export default function Reader() {
         }
     }, [curPage]);
 
+    // return spinner while chpater data is loading
     if (chapter.pageCount === -1) {
         return (
             <div className={classes.loading}>
@@ -158,6 +159,12 @@ export default function Reader() {
         }
     };
 
+    const prevChapter = () => {
+        if (chapter.index > 1) {
+            history.push(`/manga/${manga.id}/chapter/${chapter.index - 1}`);
+        }
+    };
+
     const pages = range(chapter.pageCount).map((index) => ({
         index,
         src: `${serverAddress}/api/v1/manga/${mangaId}/chapter/${chapterIndex}/page/${index}`,
@@ -181,6 +188,7 @@ export default function Reader() {
                 manga={manga}
                 chapter={chapter}
                 nextChapter={nextChapter}
+                prevChapter={prevChapter}
             />
         </div>
     );