Appending another element when a sibling element's transition ends - d3.js

Question

I have a bar chart, which I am using transitions to animate the heights of rect elements like so:
//Create a layer for each category of data that exists, as per dataPointLegend values
//e.g. DOM will render <g class="successful"><g>
layers = svg.selectAll('g.layer')
.data(stacked, function(d) {
return d.dataPointLegend;
})
.enter()
.append('g')
.attr('class', function(d) {
return d.dataPointLegend;
})
//transform below is used to shift the entire layer up by one pixel to allow
//x-axis to appear clearly, otherwise bars inside layer appear over the top.
.attr('transform', 'translate(0,-1)');
//Create a layer for each datapoint object
//DOM will render <g class="successful"><g></g><g>
barLayers = layers.selectAll('g.layer')
.data(function(d) {
return d.dataPointValues;
})
.enter()
.append('g');
//Create rect elements inside each of our data point layers
//DOM will render <g class="successful"><g><rect></rect></g></g>
barLayers
.append('rect')
.attr('x', function(d) {
return x(d.pointKey);
})
.attr('width', x.rangeBand())
.attr('y', height - margin.bottom - margin.top)
.attr('height', 0)
.transition()
.delay(function(d, i) {
return i * transitionDelayMs;
})
.duration(transitionDurationMs)
.attr('y', function(d) {
return y(d.y0 + d.pointValue);
})
.attr('height', function(d) {
return height - margin.bottom - margin.top - y(d.pointValue)
});
I then have a further selection used for appending text elements
//Render any point labels if present
//DOM will render <g><g><rect></rect><text></text></g></g>
if (width > miniChartWidth) {
barLayers
.append('text')
.text(function(d) {
return d.pointLabel
})
.attr('x', function(d) {
return x(d.pointKey) + x.rangeBand() / 2;
})
.attr('y', function(d) {
var textHeight = d3.select(this).node().getBoundingClientRect().height;
//Position the text so it appears below the top edge of the corresponding data bar
return y(d.y0 + d.pointValue) + textHeight;
})
.attr('class', 'data-value')
.attr('fill-opacity', 0)
.transition()
.delay(function(d, i) {
return i * transitionDelayMs + transitionDurationMs;
})
.duration(transitionDurationMs)
.attr('fill-opacity', 1);
}
This fades in the text elements nicely after all the rects have finished growing in height. What I wondered, was whether its possible to append a text element to the corresponding layer as each bar finishes its transition?
I have seen the answer on this SO - Show text only after transition is complete d3.js
Which looks to be along the lines of what I am after, I tried adding an .each('end',...) in my rect rendering cycle like so
.each('end', function(d){
barLayers
.append('text')
.text(function() {
return d.pointLabel
})
.attr('x', function() {
return x(d.pointKey) + x.rangeBand() / 2;
})
.attr('y', function() {
var textHeight = d3.select(this).node().getBoundingClientRect().height;
//Position the text so it appears below the top edge of the corresponding data bar
return y(d.y0 + d.pointValue) + textHeight;
})
.attr('class', 'data-value')
.attr('fill-opacity', 0)
.transition()
.delay(function(d, i) {
return i * transitionDelayMs + transitionDurationMs;
})
.duration(transitionDurationMs)
.attr('fill-opacity', 1);
});
But I end up with lots of text elements for each of my g that holds a single rect for each of my datapoints.
I feel like I'm close, but need some assistance from you wise people :)
Thanks

Answer 1

whateverTheSelectionIs
.each('end', function(d){
barLayers
.append('text')
.each runs separately for every element in your selection, and inside the each you're adding text elements to every barLayer (barLayers). So you're going to get a (barLayers.size() * selection.size()) number of text elements added overall. You need to add only one text element in the each to the right bar / g.
The below is a fudge that might work. It's tricky because the text you want to add is a sibling of the rects in the selection that calls the .each function..., d3.select(this.parentNode) should move you up to the parent of the rect, which would be the right barLayer.
whateverTheSelectionIs
.each('end', function(d,i){
d3.select(this.parentNode)
.append('text')