[improvement] extract resetScroll function (#3869)

src/utils/dom/reset-scroll.ts

@@ -0,0 +1,16 @@
+/**
+ * Hack for iOS12 page scroll
+ * https://developers.weixin.qq.com/community/develop/doc/00044ae90742f8c82fb78fcae56800
+ */
+
+import { isIOS as checkIsIOS } from '../validate/system';
+import { getRootScrollTop, setRootScrollTop } from './scroll';
+
+const isIOS = checkIsIOS();
+
+/* istanbul ignore next */
+export function resetScroll() {
+  if (isIOS) {
+    setRootScrollTop(getRootScrollTop());
+  }
+}