This has a number of problems. First, it is clearly too complicated. And this means that it isn't on just one JavaScript file. One has to use the modern horror of npm to get it (which I refuse to do). The suggested way of handling dragging doesn't work when the DOM changes, as the example below shows. There is probably some complicated way around this, but I can't be bothered given the other issues. The file that one needs to include is interact.js.