Create an Electron or NW application with local load/save functionality

Hello,

This is very impressive and useful. I'm trying it out as a replacement for the seemingly abandoned Cocoa Json Editor. I'm using http://jsoneditoronline.org/ to edit a local JSON file which is quite large. Is there a way for the save function to automatically replace the local file I opened instead of downloading a copy to my browser download directory, or is this a browser limitation? If so, how hard would it be to embed exactly what you have on the website into a standalone app or one that has access to the filesystem?

Thanks for the help.