fix: update JavaScript quickstart for clerk-js v6

[jacekradko]

Order of deployment

1. Dashboard PR
2. This PR

Summary

• Adds @clerk/ui@1 UI bundle loading to both the NPM module and <script> tag approaches
• Updates CDN references from @clerk/clerk-js@5 to @clerk/clerk-js@6
• Passes ui: { ClerkUI: window.__internal_ClerkUICtor } to clerk.load() in all code examples
• Adds VITE_CLERK_FRONTEND_API_URL env var and uses it to load the UI bundle (consistent with {{fapi_url}} in the <script> tag approach)

Context

The JavaScript quickstart guide was missing the required UI bundle loading step for @clerk/clerk-js v6. Without this, users following the guide would not see any prebuilt components rendered. The guide also referenced @clerk/clerk-js@5 in CDN URLs and derived the frontend API domain from the publishable key instead of using an env var.

Verified against the reference repo: https://github.com/jacekradko/clerk-javascript-quickstart

Test plan

• Verify the NPM module code examples work end-to-end with a fresh Vite project
• Verify the <script> tag examples work end-to-end in a plain HTML file
• Confirm prebuilt components (SignIn, UserButton) render correctly

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Project	Deployment	Actions	Updated (UTC)
clerk-docs	Ready	Preview	Mar 25, 2026 2:30pm

[SarahSoutoul]

@jacekradko Okay gave this a bit of a polish with the docs review. I'm not super keen on approving this right away for several reasons:

• The Dashboard doesn't currently display the frontend api url in the <script> as discussed in this comment, so it could confuse users to read the docs and then not actually see that in the Dashboard as the docs state.

• This right here

  

• The quickstart repo and dashboard onboarding guide also need to be updated.

@manovotny would you be able to give this a look too?

[SarahSoutoul]

@jacekradko should we be applying these changes: https://github.com/clerk/dashboard/pull/8779/changes/d99c2509a0ccb982778f4749142b836f544ca11f on here too?

[manovotny]

@jacekradko should we be applying these changes: clerk/dashboard@d99c250 on here too?

@SarahSoutoul yes, but let the reviews/changes settle there first.

[jacekradko]

@SarahSoutoul @manovotny The code examples are now aligned with the dashboard

[manovotny]

@SarahSoutoul @manovotny The code examples are not aligned with the dashboard

@jacekradko you said "not", but I'm guessing you meant "now"? cbee428 looks like alignment.

[manovotny]

Updates LGTM. @SarahSoutoul should give her 👍 too.

[SarahSoutoul]

Lets shipppp

[jacekradko]

@manovotny Yep! I totally meant NOW, not NOT 🤣