completed testing on Next V15

package.json

@@ -27,12 +27,12 @@
     "lodash": "^4.17.21",
     "moment": "^2.30.1",
     "morgan": "^1.10.0",
-    "next": "^14.2.14",
+    "next": "^15.3.2",
     "next-mdx-remote": "^5.0.0",
     "path-to-regexp": "^8.2.0",
     "qs": "^6.14.0",
-    "react": "^18.3.1",
-    "react-dom": "^18.3.1",
+    "react": "^19.1.0",
+    "react-dom": "^19.1.0",
     "react-icons": "^5.4.0",
     "rehype-autolink-headings": "^7.1.0",
     "rehype-slug": "^6.0.0",

src/app/_components/main_frame/switch.module.css

@@ -6,7 +6,7 @@
   display: inline-block;
   color: currentColor;
   border-radius: 50%;
-  border: 1.5px dashed currentColor;
+  border: 1.6px dashed currentColor;
   cursor: pointer;
   --size: 24px;
   height: var(--size);

src/app/_components/main_frame/theme-switcher.tsx

@@ -1,115 +1,92 @@
-"use client";
+'use client';
 
-import styles from "./switch.module.css";
-import { memo, useEffect, useState } from "react";
+import { memo, useEffect, useState } from 'react';
+import styles from './switch.module.css';
 
-declare global {
-  var updateDOM: () => void;
-}
+const STORAGE_KEY = 'this-theme';
+const MODES = ['system', 'dark', 'light'] as const;
+type ColorSchemePreference = typeof MODES[number];
 
-type ColorSchemePreference = "system" | "dark" | "light";
-
-const STORAGE_KEY = "this-theme";
-const modes: ColorSchemePreference[] = ["system", "dark", "light"];
-
-/** to reuse updateDOM function defined inside injected script */
-
-/** function to be injected in script tag for avoiding FOUC (Flash of Unstyled Content) */
-const NoFOUCScript = (storageKey: string) => {
-  /* can not use outside constants or function as this script will be injected in a different context */
-  const [SYSTEM, DARK, LIGHT] = ["system", "dark", "light"];
+// Injects theme script before hydration to avoid FOUC
+const noFOUCScript = (storageKey: string) => {
+  const [SYSTEM, DARK, LIGHT] = ['system', 'dark', 'light'];
+  const media = matchMedia(`(prefers-color-scheme: ${DARK})`);
 
-  /** Modify transition globally to avoid patched transitions */
-  const modifyTransition = () => {
-    const css = document.createElement("style");
-    css.textContent = "*,*:after,*:before{transition:none !important;}";
-    document.head.appendChild(css);
+  const disableTransitionsTemporarily = () => {
+    const style = document.createElement('style');
+    style.textContent = '*, *::before, *::after { transition: none !important; }';
+    document.head.appendChild(style);
 
     return () => {
-      /* Force restyle */
       getComputedStyle(document.body);
-      /* Wait for next tick before removing */
-      setTimeout(() => document.head.removeChild(css), 1);
+      setTimeout(() => document.head.removeChild(style), 1);
     };
   };
 
-  const media = matchMedia(`(prefers-color-scheme: ${DARK})`);
-
-  /** function to add remove dark class */
-  window.updateDOM = () => {
-    const restoreTransitions = modifyTransition();
-    const mode = localStorage.getItem(storageKey) ?? SYSTEM;
+  const applyTheme = () => {
+    const restoreTransitions = disableTransitionsTemporarily();
+    const storedMode = localStorage.getItem(storageKey) ?? SYSTEM;
     const systemMode = media.matches ? DARK : LIGHT;
-    const resolvedMode = mode === SYSTEM ? systemMode : mode;
+    const resolvedMode = storedMode === SYSTEM ? systemMode : storedMode;
+
     const classList = document.documentElement.classList;
-    if (resolvedMode === DARK) classList.add(DARK);
-    else classList.remove(DARK);
-    document.documentElement.setAttribute("data-mode", mode);
+    classList.toggle(DARK, resolvedMode === DARK);
+    document.documentElement.setAttribute('data-mode', storedMode);
     restoreTransitions();
   };
-  window.updateDOM();
-  media.addEventListener("change", window.updateDOM);
-};
 
-let updateDOM: () => void;
+  applyTheme();
+  media.addEventListener('change', applyTheme);
+};
 
-/**
- * Switch button to quickly toggle user preference.
- */
 const Switch = () => {
-  const [mode, setMode] = useState<ColorSchemePreference>(
-    () =>
-      ((typeof localStorage !== "undefined" &&
-        localStorage.getItem(STORAGE_KEY)) ??
-        "system") as ColorSchemePreference,
-  );
+  const [mode, setMode] = useState<ColorSchemePreference>(() => {
+    return (typeof localStorage !== 'undefined'
+      ? (localStorage.getItem(STORAGE_KEY) as ColorSchemePreference)
+      : 'system') ?? 'system';
+  });
 
   useEffect(() => {
-    // store global functions to local variables to avoid any interference
-    updateDOM = window.updateDOM;
-    /** Sync the tabs */
-    addEventListener("storage", (e: StorageEvent): void => {
-      e.key === STORAGE_KEY && setMode(e.newValue as ColorSchemePreference);
-    });
+    const storedMode = localStorage.getItem(STORAGE_KEY) as ColorSchemePreference;
+    setMode(storedMode ?? 'system');
   }, []);
 
   useEffect(() => {
     localStorage.setItem(STORAGE_KEY, mode);
-    updateDOM();
+    const systemMode = matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
+    const resolvedMode = mode === 'system' ? systemMode : mode;
+    const classList = document.documentElement.classList;
+    classList.toggle('dark', resolvedMode === 'dark');
+    document.documentElement.setAttribute('data-mode', mode);
   }, [mode]);
 
-  /** toggle mode */
-  const handleModeSwitch = () => {
-    const index = modes.indexOf(mode);
-    setMode(modes[(index + 1) % modes.length]);
+  const handleToggle = () => {
+    const nextIndex = (MODES.indexOf(mode) + 1) % MODES.length;
+    setMode(MODES[nextIndex]);
   };
+
   return (
     <button
-      suppressHydrationWarning={true}
+      suppressHydrationWarning
       className={styles.switch}
-      aria-label="ThemeSwitch"
-      onClick={handleModeSwitch}
-    >
-    </button>
+      aria-label="Toggle theme"
+      onClick={handleToggle}
+    />
   );
 };
 
 const Script = memo(() => (
   <script
+    suppressHydrationWarning
     dangerouslySetInnerHTML={{
-      __html: `(${NoFOUCScript.toString()})('${STORAGE_KEY}')`,
+      __html: `(${noFOUCScript.toString()})('${STORAGE_KEY}')`,
     }}
   />
 ));
 
-/**
- * This component wich applies classes and transitions.
- */
-export const ThemeSwitcher = () => {
-  return (
-    <>
-      <Script />
-      <Switch />
-    </>
-  );
-};
+export const ThemeSwitcher = () => (
+  <>
+    <Script />
+    <Switch />
+  </>
+);

src/app/blog/posts/[slug]/page.tsx

@@ -1,4 +1,5 @@
 // pull from private repo: [tkokhing/blog_post/_posts] MDX_FOLDER
+import { Metadata } from "next";
 import { notFound } from "next/navigation";
 import Container from "@/app/_components/container";
 import { PostHeader } from "@/app/_components/post-header";
@@ -9,7 +10,14 @@ import { generatePageStaticParams } from "@/lib/generatePageStaticParams";
 
 const MDX_FOLDER = "_posts"; 
 
-export default async function Post({ params }: { params: { slug: string } }) {
+type Params = {
+  params: Promise<{
+    slug: string;
+  }>;
+};
+
+export default async function Post(props: Params) {
+  const params = await props.params;
   const post = getPostBySlug(params.slug, MDX_FOLDER);
   if (!post) return notFound();
 
@@ -32,7 +40,8 @@ export default async function Post({ params }: { params: { slug: string } }) {
   );
 }
 
-export async function generateMetadata({ params }: { params: { slug: string } }) {
+export async function generateMetadata(props: Params): Promise<Metadata> {
+  const params = await props.params;
   return generatePageMetadata(params.slug, MDX_FOLDER);
 }
 

src/app/layout.tsx

@@ -49,14 +49,14 @@ export default function RootLayout({
   children,
 }: Readonly<{ children: React.ReactNode }>) {
   return (
-    <html lang="en">
+    <html lang="en" suppressHydrationWarning={true}>
       <body
         className={cn(inter.className, "bg-slate-50 text-sky-700 dark:bg-slate-900 dark:text-slate-300")}
       >
-        <AlertBar />
+        <ThemeSwitcher />
         <NavigationProvider>
+        <AlertBar />
           <Navigationbar />
-          <ThemeSwitcher />
           <SubpageHeader />
           <div className="min-h-screen">{children}</div>
           <Footer />

src/app/topics/AtoZ/[slug]/page.tsx

@@ -1,4 +1,5 @@
 // pull from private repo: [tkokhing/topic_post/_topics] MDX_FOLDER
+import { Metadata } from "next";
 import { notFound } from "next/navigation";
 import Container from "@/app/_components/container";
 import { PostHeader } from "@/app/_components/post-header";
@@ -9,8 +10,14 @@ import { generatePageStaticParams } from "@/lib/generatePageStaticParams";
 
 const MDX_FOLDER = "_topics"; 
 
-export default async function Post({ params }: { params: { slug: string } }) {
-  const post = getPostBySlug(params.slug, MDX_FOLDER);
+type Params = {
+  params: Promise<{
+    slug: string;
+  }>;
+};
+
+export default async function Post(props: Params) {
+  const params = await props.params;  const post = getPostBySlug(params.slug, MDX_FOLDER);
   if (!post) return notFound();
 
   return (
@@ -32,7 +39,8 @@ export default async function Post({ params }: { params: { slug: string } }) {
   );
 }
 
-export async function generateMetadata({ params }: { params: { slug: string } }) {
+export async function generateMetadata(props: Params): Promise<Metadata> {
+  const params = await props.params;
   return generatePageMetadata(params.slug, MDX_FOLDER);
 }
 

src/app/topics/AtoZ/terrified-by-linux/[slug]/page.tsx

@@ -1,4 +1,5 @@
 // pull from private repo: [tkokhing/linux_post/_linux] MDX_FOLDER
+import { Metadata } from "next";
 import { notFound } from "next/navigation";
 import Container from "@/app/_components/container";
 import { PostHeader } from "@/app/_components/post-header";
@@ -13,7 +14,14 @@ import Tip from "@/app/_components/blog_frame/tip";
 
 const MDX_FOLDER = "_linux"; 
 
-export default async function Post({ params }: { params: { slug: string } }) {
+type Params = {
+  params: Promise<{
+    slug: string;
+  }>;
+};
+
+export default async function Post(props: Params) {
+  const params = await props.params;
   const post = getPostBySlug(params.slug, MDX_FOLDER);
   const LinuxBlogComponents = {
     Tip,
@@ -41,7 +49,8 @@ export default async function Post({ params }: { params: { slug: string } }) {
   );
 }
 
-export async function generateMetadata({ params }: { params: { slug: string } }) {
+export async function generateMetadata(props: Params): Promise<Metadata> {
+  const params = await props.params;
   return generatePageMetadata(params.slug, MDX_FOLDER);
 }