HTC One X KeyCode always returns zero

I have a need to validate text entered into a textbox using JavaScript before it's sent off to a third party to be acted upon.

To do this, I'm using the browserEvent.keyCode parameter to get the keycode sent to the browser on the key-up event, then validating the code to say whether it's allowed in the textbox or not.

This works fine across all devices I've tested, apart from Chrome on the HTC One X.

I've found annoying differences between various Android and iOS devices, but they all return something that I can work with. The HTC One X, however, returns 0 with every key press apart from the Backspace and Enter keys, which return 8 and 13 respectively.

I've tried event.keyCode, event.charCode and event.which as well as browserEvent.keyCode, browserEvent.charCodeand browserEvent.which codes, and everything is returned as a 0.

Basically, I'm stuck. Does anyone have any idea

1. why the keycode is always returned as 0 on this device, and
2. how I can detect the keycode?

Although it doesn't answer the immediate question, I used some of the ideas Lukas Knuth gave me to solve it.

The process is now that a keycode of 0 is caught and handed to a function that runs the contents of the input box through some Regex validation. If the validation fails, then the last character is removed from the input box.

I apologise if anyone comes to this question seeking a solution for the HTC One X passing through 0 as the keycode, after a couple of days of research and experimentation, I couldn't find a solution, so I worked around the problem instead.