There isn't that much difference on the backend if you use Node and Typescript. ESM is the standard for JavaScript and you'll probably run into situations where

There isn't that much difference on the backend if you use Node and Typescript. ESM is the standard for JavaScript and you'll probably run into situations where you can't use a new JavaScript feature with CommonJS as early as you can with ESM. There are disadvantages and advantages to how the modules load on Node, but ESM is generally improving faster than CommonJS. If you're looking into other runtimes ESM used to be the way to go because of Deno, but these days you're likely either running Node or Bun and both work well with CommonJS and ESM. If you do both frontend and backend work, or if your team has a lot of cross-over between the two sides of the ecosystem, then it'll likely be easier for you to use ESM on both ends as CommonJS isn't supported by browsers. I think the primary reason CommonJS is still around is mostly because Typescript replaces it's import/export module system with something that's basically similar in syntax to the way ESM does it untill it gets transpiled into Javascript. If people actually had to work with CommonJS modules in 2024 then I think they'd likely go insane. Not everyone will agree with me on this, but I don't think there is a reason to rewrite old projects into ESM unless you have a very good reason to do so. That being said, there isn't really a good reason to start new projects with CommonJS either... Unless you have a really good reason to do so.