Why is there still a prevalent usage of cjs instead of the newer mjs to build?

[fwqaaq]

• I don't understand why there is such a prevalent usage of cjs instead of mjs in both scripts and packages.
• And, I believe that it's entirely possible to use mjs, and it's a more modern approach.

Who can tell me why?

[h-a-n-a]

We have a WIP PR to add this feature. See: #2168

[h-a-n-a]

you may think of some frequently used APIs like __dirname, __filename and require

Oh, maybe I got it, but I guess the above issues are not the main problems, rather they are related to some third-party dependencies, such as webpack, or some others?

Not exactly, ESM can directly import CJS modules, but if people using for example @rspack/core for their project. They have to use dynamic import to load it, which breaks the sync require semantic they might be relying on.

[fwqaaq]

I don't understand what you mean. Can respack/@core be designed using esm instead of cjs? If esm can be used in the rspack, the developers are enabled to use esm to import it. What I don't understand is why rspack uses cjs. It's not just because of __dirname, require etc., because they can be replaced with other esm methods. I haven't looked closely at rspack, I'm just curious why it's not developed using esm like vite.

[h-a-n-a]

Vite leverages conditional exports to make the package be able to work with both ESM and CJS. What's more, only a subset(async) of functions can be used for work in both formats. See: https://github.com/vitejs/vite/blob/main/packages/vite/index.cjs#L9

[h-a-n-a]

We will follow closely with webpack on adopting ESM.

[fwqaaq]

Thank you for your answer.