How do I detect hardware keyboard presence with javascript?

Question

What is the best cross-browser and cross-platform way to detect hardware keyboard presence with javascript?

Answer 1

Keyboard in JS is accessible via browser APIs which delegate to OS APIs and it's not possible to tell if there's a physical keyboard. I can cut the cord off of my physical keyboard right now, turn on virtual keyboard, click on the on-screen buttons with my mouse and the browser will still trigger every keyboard event the scripts are listening to. Form browsers's/JS's perspective the virtual keyboard is indistinguishable from a physical one.

And what does "presence" even mean? If I have a phone with a touch screen and slide-out keyboard do you expect the browser to trigger some kind of "keboardIn"/"keyboardOut" event? Same with cable plug-in/out? :)

If your app absolutely requires a physical keyboard just inform/ask the user.

Edit - after clarification by OP:

You know the facebook chat? You send messages simply by pressing "Enter", I have to show users that do not have a keyboard button to replace the "Enter" key.

So just make a form with text input and listen to the input/form events. Most (every?) soft keyboards have some kind of "Done", "Ready" or similar button. You don't need to know if the "keyCode" is equal to "13", but detect that the user has an intent to submit what he has typed. Or, as the last resort, detect f the device i touch-enabled and display the button then. ( if('ontouchstart' in document.documentElement)/* show touch sbmit button */ )