User engagement tracking on webpage

I am trying to track the engagement of an user on a web page including links clicked, time spent, depth of scrolling etc. I already know the user details as user is directed to the page by clicking on a tracked link. I searched for solutions, and came across several products including google analytics, mixpanel etc. However they seemed to be generic solutions focused more on "unknown" visitors on the site, heatmaps etc. I could be completely wrong here. Is there a javascript library that I can use which will make calls to my backend APIs to record various events? Or do I use one the above said products and get data from them to my system using APIs? Please direct me on this.