What are the potential SEO implications of using dynamic or JavaScript-based navigation menus?

Using JavaScript-based or dynamic navigation menus can definitely have some SEO implications you'll want to be aware of. The main issue is that not all search engine crawlers are equally good at rendering and accessing content within those types of menus.

While crawlers like Googlebot are getting better at handling JavaScript, there could still be cases where the crawler can't properly access the links and content behind your dynamic menus. If the crawler can't see those pages, they obviously can't get indexed and ranked.

This could lead to issues with the search engines not fully understanding your site's structure and content hierarchy. It might also prevent link equity from properly flowing through those JavaScript menu links to your important pages.

However, there are some steps you can take to ensure compatibility:

1) Provide a backup static HTML menu as well as a dynamic one, through server-side rendering or using <noscript> tags. That guarantees a crawlable version.

2) Use a headless browser service to pre-render JavaScript content into an HTML snapshot that crawlers can easily discover.

3) Look into dynamic rendering solutions like Google's Dynamic Rendering to serve a pre-rendered static version to crawlers.

4) For single-page apps, generate and submit periodic HTML snapshots through tools like Google's HTML Snapshot.

5) Make sure to still follow SEO best practices - optimized meta tags, titles, content, keywords, etc. Use structured data to help search engines understand everything.

The key is having a crawler-friendly version of your site available, in addition to the polished dynamic menus for users. With the right approach, you can get the best of both worlds without sacrificing SEO.