Javascript based internal linking

I see few SAAS that provide internal linking via javascript code. Does google recognize these dynamic links? If not then why would anyone use such services?

Google can render javascript, but it's costlier and so it tends to be a multi-step process for them to do so, eg crawl page > find javascript to execute > send to queue for later re-crawling to execute javascript
The priority that the will give to javascript rendering will depend on the relative authority of the domain.

Google can follow links that are generated via javascript, providing the links are added on the page load, and the user doesn't have to perform any actions to get them visible. Googlebot can't 'click' a navigation section to get a dropdown to show for example.

I've seen some of the SAASs that you mention, and personally I wouldn't use them. Having to execute javascript means that your pages take longer to index due to multiple crawls needed, and in this current climate indexing is a sore topic as it is. It's also a very lazy way of adding internal links - something server-side would be much better.