The problem with having so many libraries to choose from is that I don't have time to try them all out and decide which one is best suited for creating an interface similar to Falstad's (grid-based, with copy-paste-delete functionality, element highlighting on mouseover, dragging elements with the mouse, zoom in and out using the mouse, pan and center the diagram, etc.)
In any case, both Falstad's interface and mine are based on pixel-based canvas, not vector graphics using SVG.