feat(redesign): i18n language selection

[g-francesca]

preview: https://deploy-preview-2197--expressjscom-preview.netlify.app/

This PR implements internationalization (i18n) support for the Express.js documentation site with a language selector component that allows users to switch between 10 supported languages.

Key Features

• Language Selector: New dropdown component in the header to switch between supported languages (English, German, Spanish, French, Italian, Japanese, Korean, Portuguese (BR), Chinese (Simplified), Chinese (Traditional))
• i18n Infrastructure:
  • Implemented useTranslations utility to replace hardcoded content throughout the site
  • Language-specific JSON files for UI translations (astro/src/i18n/locales/)
  • Language-aware routing and content structure
• 404 Handling: Added a 404 page with i18n support to gracefully handle missing translations for specific languages

Important Notes

Large Diff Size: The PR appears very large (a lot of files under de/ content collection) because German markdown content was added for demo purposes only to showcase the full i18n functionality. These files can be removed to start with a clean folder structure if preferred. The 404 page ensures graceful fallback for missing language content.

Translation Review Needed: All UI translations in the locale JSON files were generated with AI assistance and should be reviewed by native speakers for accuracy and cultural appropriateness.

Technical Changes

• Refactored components to use i18n utilities
• Created primitive Select component used by LanguageSelect and VersionSwitcher
• Updated routing to support language-prefixed URLs (/{lang}/...)
• All hardcoded strings replaced with translation keys

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[ShubhamOulkar]

const docsCollection = defineCollection({
  loader: glob({ pattern: '**/[^_]*.{md,mdx}', base: './src/content/docs' }),
  schema: z.object({
    title: z.string(),
    description: z.string().optional(),
  }),
});

@g-francesca, Are we going to use .mdx file in future? Why underscore is excluded inside pattern?

[g-francesca]

Are we going to use .mdx file in future? Why underscore is excluded inside pattern?

@ShubhamOulkar I added mdx in case you want to use it in the future, but if this is not the case, we can remove it.
About the underscore, this is to exclude any file whose name starts with an underscore, in case you need to mark some files as draft. Let me know if you prefer to change this config.

[bjohansebas]

Technically, using MDX is ideal if we want to use components inside our Markdown, so that’s fine.

[bjohansebas]

We should add a call to action to report it in case it’s an error, like we have on the website.

[socket-security]

Review the following changes in direct dependencies. Learn more about Socket for GitHub.

Diff	Package	Supply Chain Security	Vulnerability	Quality	Maintenance	License
	npm/​@​types/​node@​25.3.0 ⏵ 25.3.2
	npm/​astro@​5.16.11 ⏵ 5.18.0	+1			+1

View full report

[bjohansebas]

While running locally, i18n works for this page. But once it’s built, it doesn’t work because the pages are static and Astro only compiles a single 404 page. I suppose that if the page weren’t static, i18n would work for this, but we can’t enable server rendering since the site is built with GitHub Actions, and changing the infrastructure isn’t something we want to do.

[bjohansebas]

LGTM, you can merge it if no one else suggests changes. It’s been a heavy week and I only had the chance to review the PR today

Important note: on the current site we have a banner saying that translations might be outdated. We shouldn’t add that in this redesign, because they actually won’t be outdated anymore since we now have automation that ensures they’re always up to date.

It’s true that we still have some mixed content, though. So instead, we should add a button at the very end like ‘Want to help translate?’ and link it to the contribution section that explains how to translate the site.

But that can be done in a future PR.

[g-francesca]

LGTM, you can merge it if no one else suggests changes. It’s been a heavy week and I only had the chance to review the PR today

Important note: on the current site we have a banner saying that translations might be outdated. We shouldn’t add that in this redesign, because they actually won’t be outdated anymore since we now have automation that ensures they’re always up to date.

It’s true that we still have some mixed content, though. So instead, we should add a button at the very end like ‘Want to help translate?’ and link it to the contribution section that explains how to translate the site.

But that can be done in a future PR.

Thank you for the review @bjohansebas. I'm merging the PR, and I've noted your comment about the help with translations.