For developing it is convenient to run locally and simply load the local file. This usually would mean loading a URL like file:///Users/username//nerdseqUIMock/index.html . But since this web app loads in other html files you get a CORE error message. Easiest way to get around this is on your computer go to your nerdseqUIMoc directory and run the following command to run a local web server:
python3 -m http.server
Then you can access the app using http://localhost:8000/index.html