I have used a combination of Mapbox GL JS examples. One to style circles with a data-driven property and another one to creating a time slider with animation.
Here's the step-by-step tutorial for #mapmadness18 challenge by @Mapbox
https://medium.com/@tayalavrinenko/maps-of-how-san-franciscans-who-use-free-wi-fi-move-652dfdb7cf6a