A file "InnerBox.js" contains a nested Drag & Drop box, and "app.js" contains main context.
At a download folder, run command "npm install"
"npm install"
After installing all packages, run command "npm start" at the folder.
"npm start"
And enter a site http://localhost:3000
At a download folder, run command "node ./server/server"
"node ./server/server"
After starting the server, connect to http://localhost:3002/api