How do I create a tree layout using JSON data in d3.v4 - without stratify()

I had the same problem. Emma's response essentially answered it, but I still had trouble getting it to work properly. I'll elaborate a bit in case anyone may find it helpful. I created a block showing the functional result here, which is based on your example data above, Emma's response, and this block.

The answer is three parts:

• You have your JSON object wrapped in Array brackets. Either remove those brackets (as I did in the gist), or put a [0] on the end of your treeData (as Emma did in the link above) to get the Object out of that 1 element Array.
• Pass your JSON object to d3.hierarchy (as Emma explained).
• Lastly, the API appears to have changed for naming the nodes, which is also taken care of in my block linked above.

For convenience, here's the code from the block I made:

var svg = d3.select("svg"),    width = +svg.attr("width"),    height = +svg.attr("height"),    g = svg.append("g").attr("transform", "translate(60,0)");var tree = d3.cluster()    .size([height, width - 160]);var stratify = d3.stratify()    .parentId(function(d) { return d.id.substring(0, d.id.lastIndexOf(".")); });d3.json("treeData.json", function(error, treeData) {  if (error) throw error;  var root = d3.hierarchy(treeData);  tree(root);  var link = g.selectAll(".link")      .data(root.descendants().slice(1))    .enter().append("path")      .attr("class", "link")      .attr("d", function(d) {        return "M" + d.y + "," + d.x            + "C" + (d.parent.y + 100) + "," + d.x            + " " + (d.parent.y + 100) + "," + d.parent.x            + " " + d.parent.y + "," + d.parent.x;      });  var node = g.selectAll(".node")      .data(root.descendants())    .enter().append("g")      .attr("class", function(d) { return "node" + (d.children ? " node--internal" : " node--leaf"); })      .attr("transform", function(d) {         return "translate(" + d.y + "," + d.x + ")";       })  node.append("circle")      .attr("r", 2.5);  node.append("text")      .attr("dy", 3)      .attr("x", function(d) { return d.children ? -8 : 8; })      .style("text-anchor", function(d) { return d.children ? "end" : "start"; })      .text(function(d) {         return d.data.name;      });});

and here's treeData.json removed from the Array:

{  "name": "Top Level",  "parent": "null",  "children": [    {      "name": "Level 2: A",      "parent": "Top Level",      "children": [        {          "name": "Son of A",          "parent": "Level 2: A"        },        {          "name": "Daughter of A",          "parent": "Level 2: A"        }      ]    },    {      "name": "Level 2: B",      "parent": "Top Level"    }  ]}

You need to run d3.hierarchy on your data to get it ready for tree(). Stratify presumably runs hierarchy or is similar in some way. So change the appropriate line to: var root = d3.hierarchy(treeData[0]);