Ability to set the prev and next key?

[kunukn]

If we want to use the up and down key instead?
or multiple keys for prev and next because the layout could change from horizontal to vertical?

It seems using the key name is supported in all modern browsers.
https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/key#example

if event.key was used instead of event.keyCode

API idea.

rovingIndex({
  element: node,   // required: the container to get roving index ux
  target: "button",    // optional: a query selector for which children should be focusable
  prev: ["ArrowUp", "ArrowLeft"], // optional: default is "ArrowLeft"
  next: ["ArrowDown", "ArrowRight"] // optional: default is "ArrowRight"
})

#4