launch_handler in manifest of PWA

launch_handler member in a Progressive Web App (PWA) manifest is part of the Launch Handler API, which allows you to control how the PWA is launched—specifically, whether it opens in a new window or reuses an existing one, and how it handles the target URL. 

{
  "name": "My PWA App",
  "start_url": "/",
  "display": "standalone",
  "launch_handler": {
    "client_mode": "focus-existing"
  }
}

• auto: The default behavior. The user agent (browser) decides the best context for the platform (e.g., navigate-existing on mobile, navigate-new on desktop).
• focus-existing: If an app instance is already running, it is brought into focus. The target URL is made available to the app via window.launchQueue but the navigation does not happen automatically, allowing you to handle it with custom JavaScript.
• navigate-existing: If an app instance is running, it is brought into focus and navigated to the launch target URL. The URL is still available via window.launchQueue for additional handling.
• navigate-new: The PWA always opens in a new web app window (or a new browsing context within the app) to load the target URL. 

if ('launchQueue' in window) {
  window.launchQueue.setConsumer(launchParams => {
    // Check if there's a target URL or files to handle
    if (launchParams.targetURL) {
      const url = new URL(launchParams.targetURL);
      // Implement custom routing or logic based on the URL
      console.log('Launched with URL:', url.pathname);
    }
    if (launchParams.files) {
      // Handle file system handles
      for (const fileHandle of launchParams.files) {
        console.log('Handling file:', fileHandle.name);
      }
    }
  });
}