Disable keyboard shrotucts on browsers

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This question is of course for each specific browser forum, but I decided to ask anyway.

I am using Phaser to develop educational game where you type letters which are analog to Sandhi/Devanagari/Sanscrit language letters. So you type ṁ or ī or ṇ, ñ, etc... and these letters are simplified by typing .m, -i, n. , ~n i.e I enter letters available on my keyboard but a special Sanscrit software analyzes these keystrokes and replaces them with appropriate    Devanagari letters.

Of course this software is not a necessity so I need to type keys from keyboard to achieve the letters above, i.e encode them.

So far I have used addKeyCapture() function to disable Space, ".", "-", and "'". Well I planned to disable Shift as well but I works somehow. Also single quote doesn't took effect as I can still open "Quick Find" box in Firefox.

gameObject.input.keyboard.addKeyCapture([32, 39, 45, 46]);

So, is there a way to disable browser keyboard shortcuts trough JavaScript without installing or configuring additional plugins, addons or browser settings?

Any ideas are welcome.

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Check this app: https://typing.io/