An attempt at Tissot's Indicatrix in d3.js v4.
It uses a spherical earth for ease of calculation, but as the earth is a slight ellipsoid, there could be a small amount of error. But this is small enough it shouldn't distort the graphics.
Each indicator circle/ellipse (depending on projection) represents a circular area with a 500 km radius. The number of indicators can be changed with the across/high variables.