Boilerplate JSON for remapping JS keycodes

jskeymap.json

{
  "Backspace": 0,
  "Tab": 0,
  "Enter": 0,
  "ShiftLeft": 0,
  "ShiftRight": 0,
  "ControlLeft": 0,
  "ControlRight": 0,
  "AltLeft": 0,
  "AltRight": 0,
  "Pause": 0,
  "CapsLock": 0,
  "Escape": 0,
  "Space": 0,
  "PageUp": 0,
  "PageDown": 0,
  "End": 0,
  "Home": 0,
  "ArrowLeft": 0,
  "ArrowUp": 0,
  "ArrowRight": 0,
  "ArrowDown": 0,
  "PrintScreen": 0,
  "Insert": 0,
  "Delete": 0,
  "Digit0": 0,
  "Digit1": 0,
  "Digit2": 0,
  "Digit3": 0,
  "Digit4": 0,
  "Digit5": 0,
  "Digit6": 0,
  "Digit7": 0,
  "Digit8": 0,
  "Digit9": 0,
  "KeyA": 0,
  "KeyB": 0,
  "KeyC": 0,
  "KeyD": 0,
  "KeyE": 0,
  "KeyF": 0,
  "KeyG": 0,
  "KeyH": 0,
  "KeyI": 0,
  "KeyJ": 0,
  "KeyK": 0,
  "KeyL": 0,
  "KeyM": 0,
  "KeyN": 0,
  "KeyO": 0,
  "KeyP": 0,
  "KeyQ": 0,
  "KeyR": 0,
  "KeyS": 0,
  "KeyT": 0,
  "KeyU": 0,
  "KeyV": 0,
  "KeyW": 0,
  "KeyX": 0,
  "KeyY": 0,
  "KeyZ": 0,
  "MetaLeft": 0,
  "MetaRight": 0,
  "ContextMenu": 0,
  "Numpad0": 0,
  "Numpad1": 0,
  "Numpad2": 0,
  "Numpad3": 0,
  "Numpad4": 0,
  "Numpad5": 0,
  "Numpad6": 0,
  "Numpad7": 0,
  "Numpad8": 0,
  "Numpad9": 0,
  "NumpadMultiply": 0,
  "NumpadAdd": 0,
  "NumpadSubtract": 0,
  "NumpadDecimal": 0,
  "NumpadDivide": 0,
  "F1": 0,
  "F2": 0,
  "F3": 0,
  "F4": 0,
  "F5": 0,
  "F6": 0,
  "F7": 0,
  "F8": 0,
  "F9": 0,
  "F10": 0,
  "F11": 0,
  "F12": 0,
  "NumLock": 0,
  "ScrollLock": 0,
  "Semicolon": 0,
  "Equal": 0,
  "Comma": 0,
  "Minus": 0,
  "Period": 0,
  "Slash": 0,
  "Backquote": 0,
  "BracketLeft": 0,
  "Backslash": 0,
  "BracketRight": 0,
  "Quote": 0
}

piano-keymap.json

{
  "Digit0": 75,
  "Digit2": 61,
  "Digit3": 63,
  "Digit5": 66,
  "Digit6": 68,
  "Digit7": 70,
  "Digit9": 73,
  "KeyB": 55,
  "KeyC": 52,
  "KeyD": 51,
  "KeyE": 64,
  "KeyG": 54,
  "KeyH": 56,
  "KeyI": 72,
  "KeyJ": 58,
  "KeyL": 61,
  "KeyM": 59,
  "KeyN": 57,
  "KeyO": 74,
  "KeyP": 76,
  "KeyQ": 60,
  "KeyR": 65,
  "KeyS": 49,
  "KeyT": 67,
  "KeyU": 71,
  "KeyV": 53,
  "KeyW": 62,
  "KeyX": 50,
  "KeyY": 69,
  "KeyZ": 48,
  "Semicolon": 63,
  "Equal": 78,
  "Comma": 60,
  "Period": 62,
  "Slash": 64,
  "BracketLeft": 77,
  "Backslash": 47,
  "BracketRight": 79
}

Keys are event.code values, key positions are those of QWERTY layout, regardless of OS's keyboard layout. Use event.key values to access the codepoint of a given key, rather than a position.