Target this->sibling with mouse event - d3.js

Question

I'm following the book Interactive Data Visualization for the Web (2nd Ed). While learning about adding interactivity to a bar chart, the text states:
Throw an invisible rect with a fill of none and pointer-events value of all on the top of each group. Even though the rect is invisible, it will still trigger mouse events, so you could have the rect span the whole height of the chart. The net effect is that mousing anywhere in that column—even in “empty” whitespace above a short blue bar—would trigger the highlight effect.
I believe I've successfully created the invisible rect in the proper place (at the end, so as to not be behind the visible rects). I can mouse anywhere in the column, even in the empty whitespace above the short blue bar. However, I cannot figure out how to only highlight the blue bar and not the entire container rect.
Fiddle
//Width and height
var w = 600;
var h = 250;
var dataset = [5, 10, 13, 19, 21, 25, 22, 18, 15, 13,
11, 12, 15, 20, 18, 17, 16, 18, 23, 25];
var xScale = d3.scaleBand()
.domain(d3.range(dataset.length))
.rangeRound([0, w])
.paddingInner(0.05);
var yScale = d3.scaleLinear()
.domain([0, d3.max(dataset)])
.range([0, h]);
//Create SVG element
var svg = d3.select("body")
.append("svg")
.attr("width", w)
.attr("height", h);
//Create groups to hold the bars and text for each data point
var groups = svg.selectAll(".groups")
.data(dataset)
.enter()
.append("g")
.attr("class", "gbar");
//Create bars
groups.append("rect")
.attr("class", "actualRect")
.attr("x", function (d, i) {
return xScale(i);
})
.attr("y", function (d) {
return h - yScale(d);
})
.attr("width", xScale.bandwidth())
.attr("height", function (d) {
return yScale(d);
})
.attr("fill", function (d) {
return "rgb(0, 0, " + Math.round(d * 10) + ")";
});
//Create labels
groups.append("text")
.text(function (d) {
return d;
})
/*.style("pointer-events", "none")*/
.attr("text-anchor", "middle")
.attr("x", function (d, i) {
return xScale(i) + xScale.bandwidth() / 2;
})
.attr("y", function (d) {
return h - yScale(d) + 14;
})
.attr("font-family", "sans-serif")
.attr("font-size", "11px")
.attr("fill", "white");
// Create container rect
// The goal is to be able to hover *above* a bar, but only highlight the visible blue bar to orange.
// I don't understand how to select (this).('actualRect'), instead of (this).("containerRect")
groups.append("rect")
.attr("class", "containerRect")
.attr("x", function (d, i) {
return xScale(i);
})
.attr("y", 0)
.attr("width", xScale.bandwidth())
.attr("height", h)
.attr("fill", "none")
.style("pointer-events", "all")
.on("mouseover", function () {
d3.select(this) // trying to target (this) -> .actualBar
.attr("fill", "orange");
});

Answer 1

You can select the sibling rect by first selecting this.parentNode from within your event callback function, and then making the desired selection.
d3.select(this.parentNode).select('.actualRect').attr("fill", "orange");
//Width and height
var w = 600;
var h = 250;
var dataset = [5, 10, 13, 19, 21, 25, 22, 18, 15, 13,
11, 12, 15, 20, 18, 17, 16, 18, 23, 25];
var xScale = d3.scaleBand()
.domain(d3.range(dataset.length))
.rangeRound([0, w])
.paddingInner(0.05);
var yScale = d3.scaleLinear()
.domain([0, d3.max(dataset)])
.range([0, h]);
//Create SVG element
var svg = d3.select("body")
.append("svg")
.attr("width", w)
.attr("height", h);
//Create groups to hold the bars and text for each data point
var groups = svg.selectAll(".groups")
.data(dataset)
.enter()
.append("g")
.attr("class", "gbar");
//Create bars
groups.append("rect")
.attr("class", "actualRect")
.attr("x", function (d, i) {
return xScale(i);
})
.attr("y", function (d) {
return h - yScale(d);
})
.attr("width", xScale.bandwidth())
.attr("height", function (d) {
return yScale(d);
})
.attr("fill", function (d) {
return "rgb(0, 0, " + Math.round(d * 10) + ")";
});
//Create labels
groups.append("text")
.text(function (d) {
return d;
})
/*.style("pointer-events", "none")*/
.attr("text-anchor", "middle")
.attr("x", function (d, i) {
return xScale(i) + xScale.bandwidth() / 2;
})
.attr("y", function (d) {
return h - yScale(d) + 14;
})
.attr("font-family", "sans-serif")
.attr("font-size", "11px")
.attr("fill", "white");
// Create container rect
// The goal is to be able to hover *above* a bar, but only highlight the visible blue bar to orange.
// I don't understand how to select (this).('actualRect'), instead of (this).("containerRect")
groups.append("rect")
.attr("class", "containerRect")
.attr("x", function (d, i) {
return xScale(i);
})
.attr("y", 0)
.attr("width", xScale.bandwidth())
.attr("height", h)
.attr("fill", "none")
.style("pointer-events", "all")
.on("mouseover", function () {
d3.select(this.parentNode).select('.actualRect').attr("fill", "orange");
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.7.0/d3.min.js"></script>
Fiddle