d3.js transition end event

Question

I am applying a transition to a group of nodes returned by selectAll(). I thought the end event would fire after all transitions finished, but each("end",function) gets called at the end of each transition.

So is there any way to set a callback that will be called after transitions on all selected node finishes ?

Should I use call for this? but I don't see it used as end callback anywhere in documentation.

also I can run a counter inside each callback. but is there any way to know how many nodes are still pending to finish transition ? or index of current node in group of selected nodes ?

I've two select() calls in chain like selectAll('.partition').selectAll('.subpartition') so index argument passed to each callback will rotated n times.

Answer 1

As far as I know there is not a built in way to know when the last transition of a group has finished but there are ways around it. One way that I have used several times involves maintaining a count of transitions that have finished.

var n = 0;

d3.selectAll('div')
   .each(function() { // I believe you could do this with .on('start', cb) but I haven't tested it
       n++;
   })
   .transition()
   .on('end', function() { // use to be .each('end', function(){})
       n--;
       if (!n) {
           endall();
       }
   })

function endall() {
    // your end function here
}

Here are the links to the relevant documentation:

• https://github.com/d3/d3-transition#control-flow
• https://github.com/d3/d3-transition#the-life-of-a-transition

Answer 2

Here's a clean way to accomplish what you want:

function endAll (transition, callback) {
    var n;

    if (transition.empty()) {
        callback();
    }
    else {
        n = transition.size();
        transition.each("end", function () {
            n--;
            if (n === 0) {
                callback();
            }
        });
    }
}

You can then easily call this function like so:

selection.transition()
    .call(endAll, function () {
        console.log("All the transitions have ended!");
    });

This will work even if the transition is empty.

Answer 3

I had the same issue

that the call back gets executed with each element

I have solved that using underscore once method

http://underscorejs.org/#once

d3.select("#myid")
.transition()
.style("opacity","0")
.each("end", _.once(myCallback) );