score:0

Just change the width - and height, because with SVG, borders are on all sides, or none - of the bar series on which you want to apply a border. E.g.

.attr("width", function(d) { return d.withBorder ? 20 : 24; })
.attr("height", function(d) { return d.height + d.withBorder ? 0 : 4; })

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