Though it is not the aim of the Mendix platform: Yes, that is possible.
First: in the browser go to the inspector (F12), go to the console and type
There you go, now you got access to a lot of information. More information on their api is is here.
Good to know: for frontend Mendix has used Dojo upto Mendix 7, but now uses React. If you have a choice between the two, better choose React.
For combining your code with the mendix frontend, check out these two Academy trainings: https://academy.mendix.com/link/path/108/Build-a-Pluggable-Widget and https://academy.mendix.com/link/path/45/Building-Custom-Widgets-(Micro-Learning)