ESLint

From: https://eslint.org/docs/latest/use/getting-started

1. Launch a codespace and browse to the commandline
2. Install it with npm init @eslint/config@latest
3. npx eslint yourfile.js
4. if 'process is not defined' error -- it isn't realizing you're executing inside of node.js, which has some global variables like 'process'; the fix is to add globals.node into the string of globals in eslint.config.js (just having languageOptions: { globals: globals.node } } was enough when I tried it last).