I'm coming from a specific use case on my side where I have an initial path and want to manipulate the object with a relative path from the initial.
After getting it working I thought it could be useful to include it on your package.

Explanation

We are going to start with this object:

constobj={a:{b:'hello',d:[{e:'world',},],},};

This PR is composed into two parts:

getByRelativePath(obj, path, relativePath)

1. I know the initial path'a.d.0'
2. I want toget the value that's relative to the initial path../../b
3. I callgetByRelativePath(obj, 'a.d.0', '../../b')
4. It should be able to step back twice ('../../' takes the context toa) and step forward once ('b' takes the context toa.b)
5. I'm expected to get'hello'

setByRelativePath(obj, path, relativePath, value)

1. I know the initial path'a.d.0'
2. I want toset the value that's relative to the initial path../../b
3. I callsetByRelativePath(obj, 'a.d.0', '../../b', 'good morning')
4. It should be able to step back twice ('../../' takes the context toa) and step forward once ('b' takes the context toa.b)
5. I'm expectedobj.a.b === 'good morning'

Note: Take into account that I'm not well knowledgeable in typescript and learned a good deal with your code. Still I know there is some work to be done on this PR related with that.

Can I get some help on that maybe? :)