react-spfx | SharePoint Framework 2016 with React Js | Frontend Framework library

I am creating an SP webpart using SPFX. The webpart needs to be able to upload multiple files either using one button or several buttons (one for each file).

I am trying to use this: https://pnp.github.io/pnpjs/sp/attachments/#add-multiple

But it doesn't show how to use it with React states. You see, I want to be able to save the file upload into state, so it can then be submitted using a button. That's when it is attached to the list item in SP. I then want the webpart to be able to display the attached item when the user clicks back on this item. This is why I need to use state.

I have read this: React SPFx - Adding files to SharePoint list field using PnPjs

and this: Handling file upload in Sharepoint List with React form

But they are not clear.

Can someone provide an example of how to use the pnpjs attachments with a React component class using state?