Regarding "require" vs "import", I find this to be a constant nightmare trying to choose one or the other. The browser and tooling for writing for the browser has all-around excellent support for using "import".

Then, at some point, I want to run some unit tests using Jest or something, and it turns into a total fucking nightmare. Each bit of tooling has certain expectations for how it expects you to import--relative vs non-relative? Do you include the .js at the end? What about .ts at the end? (That one is always "no".) Do you need .js / .mjs or .cjs / .js? Do you use ts-node? Do you want to see a warning printed to stderr every time you run Node?