feat: switch config files from .js to .mjs, env.js to env.ts and next.config.js to next.config.ts

[MaKTaiL]

Closes #2082

✅ Checklist

• I have followed every step in the contributing guide (updated 2022-10-06).
• The PR title follows the convention we established conventional-commit
• I performed a functional test on my final commit

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Changelog

• Switch .js config files to .mjs
• Switch env.js files to env.ts
• Switch next.config.js to next.config.ts

The changes were made to follow the new conventions used in create-next-app.

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Screenshots

Before:

After:

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🦋 Changeset detected

Latest commit: 4850f67

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
create-t3-app	Patch

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Name	Status	Preview	Comments	Updated (UTC)
create-t3-app	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Mar 27, 2025 7:09pm

[juliusmarminge]

.mjs is redundant when using type: module

also I don't like advocating for ts config when you can't do ESM in them...

[MaKTaiL]

.mjs is redundant when using type: module

also I don't like advocating for ts config when you can't do ESM in them...

create-next-app is currently using both .mjs and next.config.ts (even with type module)

In my opinion we should switch it as well to make it standard.

[juliusmarminge]

create-next-app is currently using both .mjs and next.config.ts (even with type module)

doesn't mean it's right ;) for example you can't do ESM in ts configs:

#2082 (comment)

[MaKTaiL]

create-next-app is currently using both .mjs and next.config.ts (even with type module)

doesn't mean it's right ;) for example you can't do ESM in ts configs:

#2082 (comment)

Alright, closing this for now.

[MaKTaiL]

@juliusmarminge This works:

I have also understood the downside of using .mjs directly. I'll keep this PR closed as changing these files is not at all necessary for now. Thanks for the explanation. 😉