Today I was working on toggling classes of elements in a d3-generated SVG, and addClass and removeClass weren't working. I verified that my selectors were correct, and also surrounded the block with a jQuery document-ready function, but no dice. I switched from using the jQuery addClass and removeClass methods to d3's classed() function, and the code magically started working!

As a further note, I imagine that the reason why this is the case is that addClass and removeClass don't recognize <path> elements, while the selectors still do.