Thank you for submitting a PR!

I noticed you removed the if statement from the code. I'd love to understand your reasoning behind that change.

Hi @thetaPC thanks for the review!

The if statement I've removed was originally added to handle the situation where delta is less than -1. In that situation what it does is return the location delta many steps back from the end of the history stack.

if (delta < -1) {
  return locationHistory[locationHistory.length - 1 + delta];
}

However, this wasn't correct behaviour. There is a routeInfo passed into the function and the returned location should be delta steps back from that. Not back from the end of locationHistory.

This is why the bug reported in the issue was happening.

I've made it so it handles both situations using that same code. This is mostly reusing the code that was in the else statement.

That code essentially searches backwards through the history stack until it finds routeInfo and returns its parent (handling the delta -1 situation). I realised I could use index of that location in the array + delta to return the correct location.

I've added tests to handle the situations and ensure the behaviour works as expected. Let me know if you need any more details :)