An experiment that shows a possible way to visually encode link directionality in node-link diagrams as animation: Some kind of "flow" moves according to the direction.
More or less related to a Mike Bostock example.
For a comparison of different methods for representing link directionality (including animated dashed lines), see Holten et al. 2010
Modified http://d3js.org/d3.v3.min.js to a secure url
https://d3js.org/d3.v3.min.js