如何在JavaScript中建立树JSON

Question

我在玩D3图表。 他们提供的示例之一是绘制树形结构的图表（ https://observablehq.com/@d3/tidy-tree ）

我按照此示例将这张图表并嵌入到Power BI中（ https://azurebi-docs.jppp.org/powerbi-visuals/d3js.html?tabs=docs%2Cdocs-open#sample ），但遇到了麻烦我目前拥有的数据。 该图表使用json作为输入（ https://raw.githubusercontent.com/d3/d3-hierarchy/v1.1.8/test/data/flare.json ）。 生成此类树结构json的脚本如下：

function toJSON(data) {
    var flare = { name: "ROOT", children: [] },
        levels = ["parentname","categoryname", "categoryname"];

    // For each data row, loop through the expected levels traversing the output tree
    data.forEach(function(d){
        // Keep this as a reference to the current level
        var depthCursor = flare.children;
        // Go down one level at a time
        levels.forEach(function( property, depth ){

            // Look to see if a branch has already been created
            var index;
            depthCursor.forEach(function(child,i){
                if ( d[property] == child.name ) index = i;
            });
            // Add a branch if it isn't there
            if ( isNaN(index) ) {
                depthCursor.push({ name : d[property], children : []});
                index = depthCursor.length - 1;
            }
            // Now reference the new child array as we go deeper into the tree
            depthCursor = depthCursor[index].children;
            // This is a leaf, so add the last element to the specified branch
            if ( depth === levels.length - 1 ) depthCursor.push({ name : d.product, size : d.revenue });
        });
    });
    // End of conversion
    return flare;
}

我面临的问题是我的数据具有不同的结构...该脚本假定level变量包含所有级别。 但是我的数据结构是这样的，每行都有一个名称（即CategoryName）和指向父表的指示符（即同一表中的ParentName）。 如此有效的记录是

CategoryName | ParentName
Category 1
Category 2 | Category 1
Category 3 | Category 2
Category 4 | Category 2

我应该如何修改提供的javascript以根据当前的数据结构构建json？

感谢您可以提供的任何支持或推荐。

编辑

数据格式为：

data = [
  {categoryname: 'Category 1', parentname: 'null'},
  {categoryname: 'Category 2', parentname: 'Category 1'},
  {categoryname: 'Category 3', parentname: 'Category 2'},
  {categoryname: 'Category 4', parentname: 'Category 2'},
];

整个PowerBI D3脚本如下所示：

/* 
 * All D3 visuals run in a frame with the following elements/variables:
 * 
 * SVG element: 
 * - <svg xmlns="http://www.w3.org/2000/svg" class="chart" id="chart" >
 * 
 * pbi object:
 * - 'dsv'    : function that retrieves the data via the provided callback: pbi.dsv(callback)
                e.g. pbi.dsv(function(data) { //Process data function });
 * - 'height' : height of the sandbox frame
 * - 'width'  : width of the sandbox frame
 * - 'colors' : color array with 8 colors; changable via options
 * 
 * Code is based on: https://bl.ocks.org/mbostock/4339083
 */

// ADD: translate function for the data 
function toJSON(data) {
    var flare = { name: "ROOT", children: [] },
        levels = ["parentname","categoryname", "categoryname"];

    // For each data row, loop through the expected levels traversing the output tree
    data.forEach(function(d){
        // Keep this as a reference to the current level
        var depthCursor = flare.children;
        // Go down one level at a time
        levels.forEach(function( property, depth ){

            // Look to see if a branch has already been created
            var index;
            depthCursor.forEach(function(child,i){
                if ( d[property] == child.name ) index = i;
            });
            // Add a branch if it isn't there
            if ( isNaN(index) ) {
                depthCursor.push({ name : d[property], children : []});
                index = depthCursor.length - 1;
            }
            // Now reference the new child array as we go deeper into the tree
            depthCursor = depthCursor[index].children;
            // This is a leaf, so add the last element to the specified branch
            if ( depth === levels.length - 1 ) depthCursor.push({ name : d.product, size : d.revenue });
        });
    });
    // End of conversion
    return flare;
}

var margin = {top: 20, right: 120, bottom: 20, left: 120},
    width = pbi.width - margin.left - margin.right,   // ALTER: Changed fixed width with the 'pbi.width' variable
    height = pbi.height - margin.top - margin.bottom; // ALTER: Changed fixed height with the 'pbi.height' variable

var i = 0,
    duration = 750,
    root;

var tree = d3.layout.tree()
    .size([height, width]);

var diagonal = d3.svg.diagonal()
    .projection(function(d) { return [d.y, d.x]; });

var svg =  d3.select("#chart")                           // ALTER: Select SVG object; no need to create it
    .attr("width", width + margin.left + margin.right)   // ALTER: Add complete width
    .attr("height", height + margin.top + margin.bottom) // ALTER: Add complete height
    .append("g")
    .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

// ALTER: Replaced the d3.json function with the pbi variant: pbi.dsv
pbi.dsv(function(data) {
    var flare = toJSON(data); // ALTER: add extra convertion step to parent/child JSON
    root = flare;
    root.x0 = height / 2;
    root.y0 = 0;

    function collapse(d) {
        if (d.children) {
            d._children = d.children;
            d._children.forEach(collapse);
            d.children = null;
        }
    }

    root.children.forEach(collapse);
    update(root);
});

d3.select(self.frameElement).style("height", height + margin.top + margin.bottom);

function update(source) {

  // Compute the new tree layout.
  var nodes = tree.nodes(root).reverse(),
      links = tree.links(nodes);

  // Normalize for fixed-depth.
  nodes.forEach(function(d) { d.y = d.depth * 180; });

  // Update the nodes…
  var node = svg.selectAll("g.node")
      .data(nodes, function(d) { return d.id || (d.id = ++i); });

  // Enter any new nodes at the parent's previous position.
  var nodeEnter = node.enter().append("g")
      .attr("class", "node")
      .attr("transform", function(d) { return "translate(" + source.y0 + "," + source.x0 + ")"; })
      .on("click", click);

  nodeEnter.append("circle")
      .attr("r", 1e-6)
      .style("fill", function(d) { return d._children ? pbi.colors[0] : pbi.colors[1]; });

  nodeEnter.append("text")
      .attr("x", function(d) { return d.children || d._children ? -10 : 10; })
      .attr("dy", ".35em")
      .attr("text-anchor", function(d) { return d.children || d._children ? "end" : "start"; })
      .text(function(d) { return d.name; })
      .style("fill-opacity", 1e-6);

  // Transition nodes to their new position.
  var nodeUpdate = node.transition()
      .duration(duration)
      .attr("transform", function(d) { return "translate(" + d.y + "," + d.x + ")"; });

  nodeUpdate.select("circle")
      .attr("r", 4.5)
      .style("fill", function(d) { return d._children ? pbi.colors[0] : pbi.colors[1]; });

  nodeUpdate.select("text")
      .style("fill-opacity", 1);

  // Transition exiting nodes to the parent's new position.
  var nodeExit = node.exit().transition()
      .duration(duration)
      .attr("transform", function(d) { return "translate(" + source.y + "," + source.x + ")"; })
      .remove();

  nodeExit.select("circle")
      .attr("r", 1e-6);

  nodeExit.select("text")
      .style("fill-opacity", 1e-6);

  // Update the links…
  var link = svg.selectAll("path.link")
      .data(links, function(d) { return d.target.id; });

  // Enter any new links at the parent's previous position.
  link.enter().insert("path", "g")
      .attr("class", "link")
      .attr("d", function(d) {
        var o = {x: source.x0, y: source.y0};
        return diagonal({source: o, target: o});
      });

  // Transition links to their new position.
  link.transition()
      .duration(duration)
      .attr("d", diagonal);

  // Transition exiting nodes to the parent's new position.
  link.exit().transition()
      .duration(duration)
      .attr("d", function(d) {
        var o = {x: source.x, y: source.y};
        return diagonal({source: o, target: o});
      })
      .remove();

  // Stash the old positions for transition.
  nodes.forEach(function(d) {
    d.x0 = d.x;
    d.y0 = d.y;
  });
}

// Toggle children on click.
function click(d) {
  if (d.children) {
    d._children = d.children;
    d.children = null;
  } else {
    d.children = d._children;
    d._children = null;
  }
  update(d);
}

Answer 1

在我看来，您的问题是XY问题的另一种情况：您不是在询问层次结构本身的问题，而是在询问您认为对于创建该层次结构所必需的功能。

您不需要该功能即可创建层次结构。 根据您的数据，您可以只使用d3.stratify ：

 const csv = `CategoryName,ParentName Category 1, Category 2,Category 1 Category 3,Category 2 Category 4,Category 2`; const data = d3.csvParse(csv); const stratify = d3.stratify() .id(function(d) { return d.CategoryName; }) .parentId(function(d) { return d.ParentName; }); let root = stratify(data); console.log(root) 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.7.0/d3.min.js"></script> 

由于您已经解析了数据，因此更加容易：

 const data = [{ categoryname: 'Category 1', parentname: '' }, { categoryname: 'Category 2', parentname: 'Category 1' }, { categoryname: 'Category 3', parentname: 'Category 2' }, { categoryname: 'Category 4', parentname: 'Category 2' }, ]; const stratify = d3.stratify() .id(function(d) { return d.categoryname; }) .parentId(function(d) { return d.parentname; }); let root = stratify(data); console.log(root) 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/5.7.0/d3.min.js"></script> 

PS：使用浏览器的控制台检查root对象，而不是检查堆栈片段。