How to alow users to edit json files

I would like to alow people to edit json files without giving access to my project. How would I do that? I was thinking of building a /user/modify.html page with all of the imputs of their json file? How would I do that? I found an an answer here: javascript - How to update user inputted data into JSON - Stack Overflow but I have no idea how to implement that in to a page.

This post from SteGriff describes one way to set it up:

The Stack Overflow question you linked to looks like an Express route. If you are unsure of how they work, I would recommend you take a look here:

To read / write your JSON file you can use the Node module fs. To read the file use readFile, to write use writeFile.