Algorithm to extract outer SVG path [duplicate]

Question

I'd like to extract the outer path (red line) of A and B circles (or other paths/shapes), and erase all the inner lines, so there would be only one path (perhaps a little bit of a complicated one). Is there any algorithm that could do this easily?

_{(source: candelalearning.com)}

Answer 1

The term you are looking for is bezier path boolean operations, specifically union for the case you are presenting (this should help you googling).

Paper.js has a javascript implementation:

You can see the examples here.