Programmatically open nested, collapsed (hidden) nodes in d3.js v4

Question

I am trying to programmatically open d3.js nodes in a collapsible tree:

I load the data with the following d3.js snippet (which collapses the nodes after the second level),

d3.json("js/ontology.json", function(error, treeData) {
  if (error) throw error;
  root = d3.hierarchy(treeData, function(d) { return d.children; });
  root.x0 = height / 2;
  root.y0 = 0;
  // Collapse after the second level:
  root.children.forEach(collapse);
  update(root);
});

I then use the following d3.js code

var nodeEnter = node.enter().append('g')
    .attr('class', 'node')
    .attr('node-name', d => d.data.name.toLowerCase())
    .attr("transform", function(d) {
      return "translate(" + source.y0 + "," + source.x0 + ")";
  })
.on('click', click);

and this function

function expandNode() {
  const node = d3.select('.node[node-name="Nature"]').node();
  console.log('NODE: ', node);
  node.dispatchEvent(new Event('click'));
  }
expandNode();

to programmatically open the "Nature" node.

However, when I substitute "Nature" (visible node) with "Earth" (nested child of "Nature", not visible) this expression

const node = d3.select('.node[node-name="Earth"]').node();

will expand the "Earth" node only if it is visible.

That statement will not expand "Nature" to show "Earth" (and subsequently expand "Earth") if "Earth" is not visible.

Suggestions?

---

Edit 1. This is closely related to my earlier StackOverflow question,

Programmatically opening d3.js v4 collapsible tree nodes?

If needed, please refer to the JSFiddle referenced there,

https://jsfiddle.net/vstuart/acx5zfgn/62/

The labels are different but otherwise the data and code are similar.

---

Edit 2. Follow-on question

Accessing promised data in d3.js v6 [programmatically opening nested collapsed nodes]

relating to:

• d3.js v6;
• loading external JSON data via d3.js callback/promise;
• this question, in that updated context.

---

ontology.json

{ "name": "Root",
  "children": [
    { "name": "Culture",
      "children": [
        { "name": "LGBT" }
      ]
    },

    { "name": "Nature",
      "id": "nature",
      "children": [
        { "name": "Earth",
          "id": "earth",
          "children": [
            { "name": "Environment" },
            { "name": "Geography" },
            { "name": "Geology" },
            { "name": "Geopolitical" },
            { "name": "Geopolitical - Countries" },
            { "name": "Geopolitical - Countries - Canada" },
            { "name": "Geopolitical - Countries - United States" },
            { "name": "Nature" },
            { "name": "Regions" }
          ]
        },
        { "name": "Cosmos" },
        { "name": "Outer space" }
      ]
    },

    { "name": "Humanities",
      "children": [
          { "name": "History" },
          { "name": "Philosophy" },
          { "name": "Philosophy - Theology" }
      ]
    },

    { "name": "Miscellaneous",
      "children": [
          { "name": "Wikipedia",
            "url": "https://wikipedia.com" },
          { "name": "Example.com",
            "url": "https://example.com" }
      ]
    },
      
    { "name": "Science",
      "children": [
          { "name": "Biology" },
          { "name": "Health" },
          { "name": "Health - Medicine" },
          { "name": "Sociology" }
      ]
    },

    { "name": "Technology",
      "children": [
            { "name": "Computers" },
            { "name": "Computers - Hardware" },
            { "name": "Computers - Software" },
            { "name": "Computing" },
            { "name": "Computing - Programming" },
            { "name": "Internet" },
            { "name": "Space" },
          { "name": "Transportation" }
      ]
    },

  { "name": "Society",
      "children": [
            { "name": "Business" },
            { "name": "Economics" },
            { "name": "Economics - Business" },
            { "name": "Economics - Capitalism" },
            { "name": "Economics - Commerce" },
            { "name": "Economics - Finance" },
            { "name": "Politics" },
          { "name": "Public services" }
      ]
    }
  ]
}

Answer 1

You need to discover the node ancestors recursively and then expand them on by one:

const findNodeAncestors = (root, name) => {
  if (root.name === name) {
    return [name];
  }

  if (root.children) {
    for (let i = 0; i < root.children.length; i++) {
      const chain = findNodeAncestors(root.children[i], name);
      if (chain) {
        chain.push(root.name);
        return chain;
      }
    }
  }
  return null;
}; 
   

const chain = findNodeAncestors(treeData.data, 'Earth');
  
for (let i = chain.length - 1; i >= 0; i--) {
  const node = d3.select(`.node[node-name="${chain[i]}"]`);
  const nodeData = node.datum();
  if (!nodeData.children && nodeData.data.children) {  // Node has children and collapsed
    node.node().dispatchEvent(new Event('click'));     // Expand the node
  }
}

See it's working in a fiddle .