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Asked: 2026-06-04T03:28:55+00:00

I’ve created the following document: <g> <path class=​"line" name=​"gene_1" stroke=​"#aec7e8" d=​"M10.47…">​</path>​ <path class=​"line" name=​"gene_2"

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I’ve created the following document:

<g>
    <path class=​"line" name=​"gene_1" stroke=​"#aec7e8" d=​"M10.47...">​</path>​
    <path class=​"line" name=​"gene_2" stroke=​"#aec7e8" d=​"M10.47...">​</path>​
    <path class=​"line" name=​"gene_3" stroke=​"#aec7e8" d=​"M10.47...">​</path>​
    ...
</g>

When I mouse over each path I want to append it last inside the svg:g so it appears on top of the other lines, but I don’t know how to properly select the parentNode:

function onmouseover(d, i){
  var current_gene_name = d3.select(this).attr("name"),
      current_gene_pcp = d3.select(".line[name=" + current_gene_name + "]");

  p1 = this.parentNode 

  p2 = current_gene_pcp[0].parentNode

  p3 = current_gene_pcp[0][0].parentNode

  //p.appendChild(this);
}

p1 works, but I wanted to make sure that this is a .line, so I preferred to use current_gene_pcp, but p2 returns <html></html> as the parent, even though p3 returns the proper <g></g>. This last version seems like a bug waiting to happen. Is there a better way?

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1 Answer

  1. Editorial Team

    A D3 selection is just a double-array wrapped around the element(s) selected. As you found with p3, you can dereference the arrays to find your first node, if you want. However, a better method does exist:

    From the docs for selection.node():

    Returns the first non-null element in the current selection. If the selection is empty, returns null.

    In your case:

    var dad = current_gene_pcp.node().parentNode;

    However, if you don’t need the line other than the DOM handle, you might as well just get that directly:

    // Search document-wide...
var dad = document.querySelector(".line[name=" + current_gene_name + "]");

// ...or only as a child of the current DOM element
var dad = this.querySelector(".line[name=" + current_gene_name + "]");
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