I used to work for a company where it was ok (managers won't say anything, even if explicitly pointed at the situation) to remove company company code, create your own NPM package (on your own private NPM account) and add it as a dependency of the company codebase(s).
This and some other similar behaviours were the reason I left that company. But I'm the loser of the story here, as those guys are now working for even bigger companies with bigger salaries than me.