You can clone the final project to look at the source and play around with it:
write-fs-from-the-client-js.boomla.net
This intro shows how to write the Filesystem from JavaScript code that runs in the browser.
It has two parts:
There is an API endpoint at /api/create-file
(that we write ourselves), and
a client side JS code that is calling the API endpoint, which is at /paper-with-1-column-3/code/script.js
We are using jQuery for selecting the DOM elements and sending AJAX POST requests to the server.
The files that are created are stored under /entries
.
If you are not an experienced programmer, you might want to consider using a simple form instead and creating the files on the server side similar to the TODO list app example.