I'm working on a web application where I need to detect if the user is on Firefox because it behaves differently when closing a specific window compared to Google Chrome. Right now, the codebase uses the following method to check for Firefox:

var isFirefox = typeof InstallTrigger !== 'undefined';

This detection is used in multiple .html, .js files, mostly for:

• File and folder handling (uploading, removing files, browsing folders)
• UI adjustments (fixing rendering or event handling issues)
• Closing specific windows (Firefox behaves differently from Chrome when closing windows)

The detection is also often paired with:

navigator.userAgent.search("Chrome")

My Questions:

1. Is typeof InstallTrigger !== 'undefined' still a reliable way to detect Firefox?
2. Would a different approach, like feature detection, be better for handling browser-specific window closing behavior?
3. What’s the best way to handle cross-browser differences when closing a window?

I’d really appreciate any advice on the best way to handle this! Thanks in advance!