Convert JavaScript to TypeScript for improved type safety and maintainability

.devcontainer/devcontainer.json

@@ -0,0 +1,17 @@
+{
+  "name": "Split Translator Development",
+  "image": "mcr.microsoft.com/devcontainers/javascript-node:22-bookworm",
+  "features": {
+    "ghcr.io/devcontainers/features/github-cli:1": {}
+  },
+  "postCreateCommand": "npm install",
+  "customizations": {
+    "vscode": {
+      "extensions": [
+        "github.vscode-github-actions",
+        "ms-vscode.vscode-typescript-next"
+      ]
+    }
+  },
+  "remoteUser": "node"
+}

.github/workflows/copilot-setup-steps.yml

@@ -0,0 +1,33 @@
+name: "Copilot Setup Steps"
+
+on:
+  workflow_dispatch:
+  push:
+    paths:
+      - .github/workflows/copilot-setup-steps.yml
+  pull_request:
+    paths:
+      - .github/workflows/copilot-setup-steps.yml
+
+jobs:
+  # The job MUST be called `copilot-setup-steps` or it will not be picked up by Copilot.
+  copilot-setup-steps:
+    runs-on: ubuntu-latest
+
+    permissions:
+      contents: read
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: "22"
+
+      - name: Install JavaScript dependencies
+        run: npm install
+
+      - name: Build TypeScript project
+        run: npm run build

README.md

@@ -110,21 +110,57 @@ split-translator/
 | **Screen Resolution** | Minimum width of 800px is recommended |
 | **Browser Version** | Chrome 88+, Edge 88+ (Manifest V3 required) |
 
-## 🛠️ Development & Customization
+## 🛠️ Development & Building
 
-### Adjusting Window Overlap
-```javascript
-const OVERLAP_PIXELS = 8; // Adjustable in background.js
+This extension is built with **TypeScript** for enhanced type safety and maintainability.
+
+### Prerequisites
+- Node.js (v22 or higher)
+- npm
+
+### Building from Source
+```bash
+# Install dependencies
+npm install
+
+# Build TypeScript to JavaScript
+npm run build
+
+# Clean build directory
+npm run clean
+
+# Watch for changes during development
+npm run watch
+
+# Build and package for distribution
+npm run package
+```
+
+### Project Structure
+```
+src/
+  ├── background.ts    # Service worker (TypeScript)
+  ├── popup.ts         # Popup script (TypeScript)
+dist/
+  ├── background.js    # Compiled service worker
+  ├── popup.js         # Compiled popup script
+```
+
+### Development & Customization
+
+#### Adjusting Window Overlap
+```typescript
+const OVERLAP_PIXELS = 8; // Adjustable in src/background.ts
 ```
 
-### Adding a Language
+#### Adding a Language
 ```html
 <!-- Add to the <select> element in popup.html -->
 <option value="new_language_code">🏁 New Language Name</option>
 ```
 
-### Timeout Setting
-```javascript
+#### Timeout Setting
+```typescript
 await waitForTabReady(tabId, 3000); // 3 seconds timeout
 ```
 

build-package.bat

@@ -13,7 +13,7 @@ if exist "dist\split-translator.zip" del "dist\split-translator.zip"
 echo [*] Creating package...
 
 REM Create ZIP file using PowerShell
-powershell -Command "& { Add-Type -AssemblyName System.IO.Compression.FileSystem; $zip = [System.IO.Compression.ZipFile]::Open('dist\split-translator.zip', 'Create'); $files = @('manifest.json', 'popup.html', 'popup.js', 'background.js', 'LICENSE', 'PRIVACY_POLICY.md'); foreach ($file in $files) { if (Test-Path $file) { [System.IO.Compression.ZipFileExtensions]::CreateEntryFromFile($zip, $file, $file) | Out-Null; Write-Host \"+ $file\" } }; if (Test-Path 'icons') { Get-ChildItem 'icons\*.png' | ForEach-Object { [System.IO.Compression.ZipFileExtensions]::CreateEntryFromFile($zip, $_.FullName, 'icons\' + $_.Name) | Out-Null; Write-Host \"+ icons\$($_.Name)\" } }; $zip.Dispose() }"
+powershell -Command "& { Add-Type -AssemblyName System.IO.Compression.FileSystem; $zip = [System.IO.Compression.ZipFile]::Open('dist\split-translator.zip', 'Create'); $files = @('manifest.json', 'popup.html', 'dist\popup.js', 'dist\background.js', 'LICENSE', 'PRIVACY_POLICY.md'); foreach ($file in $files) { if (Test-Path $file) { [System.IO.Compression.ZipFileExtensions]::CreateEntryFromFile($zip, $file, $file) | Out-Null; Write-Host \"+ $file\" } }; if (Test-Path 'icons') { Get-ChildItem 'icons\*.png' | ForEach-Object { [System.IO.Compression.ZipFileExtensions]::CreateEntryFromFile($zip, $_.FullName, 'icons\' + $_.Name) | Out-Null; Write-Host \"+ icons\$($_.Name)\" } }; $zip.Dispose() }"
 
 echo.
 echo [OK] Package created successfully: dist\split-translator.zip

manifest.json

@@ -22,7 +22,7 @@
     }
   },
   "background": {
-    "service_worker": "background.js"
+    "service_worker": "dist/background.js"
   },
   "icons": {
     "16": "icons/icon-16.png",

package.json

@@ -12,7 +12,11 @@
     "url": "https://github.com/SIkebe/split-translator/issues"
   },
   "scripts": {
-    "package": "build-package.bat"
+    "build": "tsc",
+    "watch": "tsc --watch --preserveWatchOutput",
+    "package": "npm run build && build-package.bat",
+    "clean": "rimraf dist",
+    "dev": "npm run clean && npm run build && echo 'Development build complete. Load dist/ folder in Chrome Extensions.'"
   },
   "keywords": [
     "browser-extension",
@@ -31,13 +35,15 @@
   },
   "license": "MIT",
   "devDependencies": {
-    "@types/chrome": "0.0.329"
+    "@types/chrome": "0.0.329",
+    "rimraf": "6.0.1",
+    "typescript": "5.8.3"
   },
   "files": [
     "manifest.json",
     "popup.html",
-    "popup.js",
-    "background.js",
+    "dist/popup.js",
+    "dist/background.js",
     "icons/",
     "LICENSE",
     "PRIVACY_POLICY.md",

popup.html

@@ -228,6 +228,6 @@ <h1>Split Translator</h1>
     </div>
   </main>
 
-  <script src="popup.js"></script>
+  <script src="dist/popup.js"></script>
 </body>
 </html>

background.js → src/background.ts

@@ -1,12 +1,16 @@
 // Background script (Service Worker)
 
+/// <reference path="shared-types.ts" />
+
 // Constants
 const OVERLAP_PIXELS = 8; // Compensate for window frame gaps
 const MIN_WINDOW_WIDTH = 400; // Minimum window width in pixels
 const MIN_WINDOW_HEIGHT = 300; // Minimum window height in pixels
+const DEFAULT_WINDOW_WIDTH = 800; // Default window width when current window width is unavailable
+const DEFAULT_WINDOW_HEIGHT = 600; // Default window height when current window height is unavailable
 
 // Common error handler
-function handleError(error, context) {
+function handleError(error: Error, context: string): { success: false; error: string } {
   console.error(`${context}:`, error);
   return {
     success: false,
@@ -15,7 +19,7 @@ function handleError(error, context) {
 }
 
 // Message listener
-chrome.runtime.onMessage.addListener((request, sender, sendResponse) => {
+chrome.runtime.onMessage.addListener((request: SplitAndTranslateMessage, sender, sendResponse) => {
   if (request.action === 'splitAndTranslate') {
     handleSplitAndTranslate(request.currentTab, request.targetLanguage)
       .then(result => sendResponse(result))
@@ -25,7 +29,7 @@ chrome.runtime.onMessage.addListener((request, sender, sendResponse) => {
 });
 
 // Split view handling
-async function handleSplitView(currentTab, targetLanguage) {
+async function handleSplitView(currentTab: chrome.tabs.Tab, targetLanguage: string): Promise<{ success: true }> {
   try {
     console.log('Starting split view:', currentTab);
 
@@ -44,8 +48,8 @@ async function handleSplitView(currentTab, targetLanguage) {
       'file://',
     ];
 
-    if (UNSUPPORTED_PREFIXES.some(prefix => currentTab.url.startsWith(prefix)) ||
-        currentTab.url.includes('translate.goog')) {
+    if (UNSUPPORTED_PREFIXES.some(prefix => currentTab.url!.startsWith(prefix)) ||
+        currentTab.url!.includes('translate.goog')) {
       throw new Error('This page type cannot be translated. Please try on a regular website.');
     }
 
@@ -71,14 +75,14 @@ async function handleSplitView(currentTab, targetLanguage) {
     const rightWidth = halfWidth + OVERLAP_PIXELS;
 
     // Calculate positions (use entire display)
-    const leftPosition = {
+    const leftPosition: WindowPosition = {
       left: displayLeft,
       top: displayTop,
       width: leftWidth,
       height: displayHeight
     };
 
-    const rightPosition = {
+    const rightPosition: WindowPosition = {
       left: displayLeft + halfWidth - OVERLAP_PIXELS,
       top: displayTop,
       width: rightWidth,
@@ -96,15 +100,19 @@ async function handleSplitView(currentTab, targetLanguage) {
       state: 'normal'
     });
 
+    if (!rightWindow || !rightWindow.tabs || !rightWindow.tabs[0]?.id || !rightWindow.id) {
+      throw new Error('Failed to create right window');
+    }
+
     // Resize left window
     await chrome.windows.update(currentTab.windowId, {
       ...leftPosition,
       state: 'normal'
     });
 
     // Save data
-    const splitViewData = {
-      originalTabId: currentTab.id,
+    const splitViewData: SplitViewData = {
+      originalTabId: currentTab.id!,
       duplicatedTabId: rightWindow.tabs[0].id,
       targetLanguage: targetLanguage,
       originalWindowId: currentTab.windowId,
@@ -122,12 +130,12 @@ async function handleSplitView(currentTab, targetLanguage) {
 }
 
 // Execute split view and translation at once
-async function handleSplitAndTranslate(currentTab, targetLanguage) {
+async function handleSplitAndTranslate(currentTab: chrome.tabs.Tab, targetLanguage: string): Promise<{ success: true }> {
   try {
     console.log('Starting split view + translation:', currentTab);
 
     // Prepare translation URL in advance (for parallel processing)
-    const translateUrl = `https://translate.google.com/translate?sl=auto&tl=${targetLanguage}&u=${encodeURIComponent(currentTab.url)}`;
+    const translateUrl = `https://translate.google.com/translate?sl=auto&tl=${targetLanguage}&u=${encodeURIComponent(currentTab.url!)}`;
 
     // 1. Execute split view
     await handleSplitView(currentTab, targetLanguage);
@@ -148,7 +156,7 @@ async function handleSplitAndTranslate(currentTab, targetLanguage) {
     const currentUrl = rightTab.url;
 
     // Do nothing if URL is already Google Translate page
-    if (currentUrl.includes('translate.google.com')) {
+    if (currentUrl && currentUrl.includes('translate.google.com')) {
       console.log('Right tab is already a Google Translate page');
       return { success: true };
     }
@@ -176,7 +184,7 @@ async function handleSplitAndTranslate(currentTab, targetLanguage) {
 }
 
 // Get display information (helper function)
-async function getDisplayInfo() {
+async function getDisplayInfo(): Promise<chrome.system.display.DisplayUnitInfo[]> {
   if (!chrome.system?.display) return [];
 
   return new Promise((resolve) => {
@@ -192,7 +200,7 @@ async function getDisplayInfo() {
 }
 
 // Wait for tab to finish loading (helper function)
-async function waitForTabReady(tabId, maxWaitTime = 3000) {
+async function waitForTabReady(tabId: number, maxWaitTime: number = 3000): Promise<void> {
   const startTime = Date.now();
   while (Date.now() - startTime < maxWaitTime) {
     try {
@@ -206,7 +214,7 @@ async function waitForTabReady(tabId, maxWaitTime = 3000) {
 }
 
 // Helper function to enforce minimum dimensions
-function enforceMinimumDimensions(bounds) {
+function enforceMinimumDimensions(bounds: DisplayBounds): DisplayBounds {
   return {
     ...bounds,
     width: Math.max(bounds.width, MIN_WINDOW_WIDTH),
@@ -215,22 +223,22 @@ function enforceMinimumDimensions(bounds) {
 }
 
 // Get display bounds (helper function)
-function getDisplayBounds(displays, currentWindow) {
-  let bounds;
+function getDisplayBounds(displays: any[], currentWindow: chrome.windows.Window): DisplayBounds {
+  let bounds: DisplayBounds;
 
   if (!displays || !displays.length) {
     console.warn('No display information available, using current window bounds');
     bounds = {
-      left: currentWindow.left, // Preserve current window position
-      top: currentWindow.top,  // Preserve current window position
-      width: currentWindow.width,
-      height: currentWindow.height
+      left: currentWindow.left ?? 0, // Preserve current window position
+      top: currentWindow.top ?? 0,  // Preserve current window position
+      width: currentWindow.width ?? DEFAULT_WINDOW_WIDTH,
+      height: currentWindow.height ?? DEFAULT_WINDOW_HEIGHT
     };
   } else {
     // Find the display to which the current window belongs
     // Use window center point for accurate detection
-    const windowCenterX = currentWindow.left + (currentWindow.width / 2);
-    const windowCenterY = currentWindow.top + (currentWindow.height / 2);
+    const windowCenterX = (currentWindow.left ?? 0) + ((currentWindow.width ?? DEFAULT_WINDOW_WIDTH) / 2);
+    const windowCenterY = (currentWindow.top ?? 0) + ((currentWindow.height ?? DEFAULT_WINDOW_HEIGHT) / 2);
 
     const display = displays.find(d =>
       windowCenterX >= d.workArea.left &&