When creating a progressive web app how can i know that a mobile device is connected to a working internet connection cause it can be connected but not working.
The saying, "You never know until you try" is pertinent here. At the moment you want to check whether there is connectivity, simply fetch a remotely hosted resource with a cache-busting technique. It's generally best practice for that resource to be tiny in file size if you need to check regularly and often (such as 1×1 pixel gif). If you receive a network response in the 200 range, you have connectivity. Otherwise, for the moment at least, you probably don't.