access what is set by the selectin.on()

[lanyjie]

I wonder if it is possible to access the event handler set by the selection.on() method. I tried quite a few but all failed. for example, I would like to blink a path by repeatedly call the same transition function:

d3.select('#sensor')
.on('mouseover', function(){
d3.select('#actor')
.transition()
.each('start', function(){d3.select(this).attr('stroke-width',1); })
.attr('stroke-width', 4).delay(1000)
.each('end', function(){ this.onmoueover(); })

The intention of the above code is to recursively call the function set by the on() method. Is there anyway to get it done? I also tried to use selection.on('mouseover') to access the set function, without luck.

Regards,

Lane

[mbostock]

There's on API for doing this currently, but you can access where we store the handler: this.__onmouseover. If you use a namespaced handler, then it's this["__onmouseover.name"].

Another thing you can do that's easy is to not use an anonymous function, and just call your function. For example:

d3.select("#sensor").on("mouseover", mouseover);
d3.select("#actor").transition().each("end", mouseover);

function mouseover() {
  // do some stuff here
}

Lastly, issue #100 covers a request to trigger events on other objects, which would be another way of calling their event handlers. In this case, you could trigger a "mouseover" event on the desired elements, and all the associated event handlers would be run.

[lanyjie]

Thanks, that surely solves my problem. I used a named function, but your code reads much better, I didn't realized that you can also modify the transition (created in mouseover function) by doing something like:

d3.select("#actor").transition().each("end", mouseover);

Very cool. I wonder if it is a good design to have the .on('mouseover') call to return the previously set mouseover handler? this works like the way of .attr() calls, sounds quite intuitive. Using this.__onmouseover is like working beneath the hood, which requires much knowledge of the implementation.

[mbostock]

Yeah, it'd be nice if .on("mouseover") returned the mouseover handler.

[mbostock]

Fixed in 2.0.0. @a4500fcfb112a011a59c123b000508cb326b453a