Managing configs for client-side npm modules - is there a preferred/standard way to go about this?

My primary question is whether or not the 'config' should be in a separate JSON/rc format, or if a general withCustomConfig-like function makes more sense. I realize this may be a matter of opinion, but I'm interested in hearing what more experienced developers think, as my searches for more information on this topic are coming up completely empty and I'm sure there's a preferred/standard way of handling something like this.

Essentially, I'm building an npm package for the generation/parsing of markdown for a specific use-case. The package allows for custom configurations to the characters utilized in the structure of the markdown itself. Originally, I was just intending on having users apply changes to the config via a simple withCustomConfig function (that accepts a config object); however, I started wondering if setting it via a JS function was not ideal - as the config's state then generally appears to seem more transient/loosely-defined than a completely separate rc or JSON config. I realize that is a matter of perception, but I think many people would share the same sentiment. And this poses a large risk because any changes to the configuration post-production would result in existing markdown becoming unparseable.

So, I started looking into having users configure a separate JSON config file. In order to import that into the browser, I realized I'd have to parse the JSON and convert it into a JS module before the user builds their client side application, which was relatively easy thanks to packages like fs. I set-up a small CLI utility to regenerate the JS module and added a postinstall script which parses the 开发者_JAVA技巧config file.

Then I started wondering if I was over-engineering this library, considering it's bound to be a relatively small aspect in its users' application. I started wondering if it even really warranted a completely separate config file and all the logic associated with parsing that for the browser. In general, would a simple withCustomConfig function actually be preferred/more-standard, or would an rc file be preferred by most people in this use case?