[chrismorgan]

I thought about it a bit longer after I wrote it and decided that what you need is some sort of pure function that takes the event target DOM element only, and decides whether the default should be prevented. For example, in FastMail we use a function to intercept links that will essentially check whether the href is routable (fiddlier than you might guess, unfortunately) and not target=_blank; that could be reduced to such a pure function, though various routes would now need to be specified in two places. Either that, or just always pipe generated <a href> elements through some function in the worker that annotates them—I like your idea, thanks for the thoughts!

Either way, I can’t think of anything where you need fully conditional preventDefault. Definitely something closer to declarative than imperative is good for these sorts of things.