useRef / useMemo in Stream.tsx

src/js/components/Stream.tsx

@@ -1,4 +1,4 @@
-import React, { useEffect } from "react";
+import React, { useEffect, useMemo, useRef } from "react";
 import * as Quran from "lib/Quran";
 import { AudioControl } from "components/AudioControl";
 import { formatNumber, TFunction } from "lib/i18n";
@@ -26,7 +26,9 @@ export function Stream({
   const className = classNames("body", "stream");
   const style: React.CSSProperties =
     endOfStream || isPaused ? { overflowY: "auto" } : { overflowY: "hidden" };
-  const ayat = stream.map((ayah: Quran.Ayah) => {
+  const ul = useRef<HTMLUListElement>();
+  const ayat = useMemo<JSX.Element[]>(() => {
+    return stream.map((ayah: Quran.Ayah) => {
       return (
         <li key={ayah.id} className="ayah fade">
           <span className="title">
@@ -48,15 +50,19 @@ export function Stream({
         </li>
       );
     });
-
-  useEffect(() => {
-    const ul: HTMLElement = document.querySelector("ul.stream")!;
-    const top = ul.offsetHeight + ul.scrollTop;
-    ul.scrollBy({ behavior: "smooth", top });
   }, [stream.length]);
 
+  useEffect(() => {
+    const el = ul.current;
+    if (el) {
+      const top = el.scrollHeight + el.scrollTop;
+      el.scrollTo({ behavior: "smooth", top });
+      el.scrollIntoView({ behavior: "smooth" });
+    }
+  }, [ul.current, stream.length]);
+
   return (
-    <ul lang={locale} className={className} style={style}>
+    <ul lang={locale} className={className} style={style} ref={ul}>
       {ayat}
     </ul>
   );