theme.js not working after "npm run"

[Magnusvb]

Hi

I started to build my own theme (from Classic) on Prestashop 1.7.6. But after updating to 1.7.8 the cart was "broken": Changing quantity does no longer update the total amount. After some trial and error, I  replace all the cart and checkout templates from the the Classic theme (1.7.8) and also al the theme's js files.

So here is the issue:
1. Copy the file theme.js from themes/classic/assets/js the quantity changes works (in my custom theme).
2. Then, running "npm run watch" in the Terminal (MacOS), then quantity changes does not works anymore.
3. Back to #1 and copy again - and it's working again. 🙄

Question: what else do I need to update/replace to get the compiled theme.js correct and the same as in the Classic theme?

/ Magnus

Edited March 7, 2022 by Magnusvb
Spelling error in the title (see edit history)