Does anyone know how I could accomplish a per frame callback for a transition with D3. Here is and example of what I am doing currently.

link.transition()
    .duration(duration)
    .attr("d", diagonal)
    .each("end",function(e) {
        if(e.target.id == current)
            show_tooltip(e.target)
    });

This currently calls the anonymous function for each element at the end of the animation. I would like to call it for every frame.