I am using a node app that displays stls online & analyzes them. Is it possible to determine the minimum wall thickness of the stl just like 3D Hubs print analyzer does?
An STL file is a surface model file. From Wikipedia you can read that:
STL files describe only the surface geometry of a three-dimensional object without any representation of color, texture or other common CAD model attributes.
This implies that there is no such thing as a wall thickness, as such you will not be able to determine the wall thickness (it is infinitesimally small). You might be interested in part thickness at a certain position; part thickness and wall thickness for 3D printing are determined when the STL model is sliced into sliced for creating 3D printer code.