在 D3 中悬停时将以前的链接设置为 child

Question

我正在 D3.js 中制作树形图。

当我将鼠标放在 child 矩形（图片上 = 红点）上时，我尝试修改先前链接的颜色（图片上 = 蓝线）。

有没有办法在触发矩形上的悬停事件时访问链接路径？

Answer 1

在下面，您可以看到另一个问题中的 v3 的 d3 v6 版本。

v6 示例取自此 block，但添加了 'path tracing'。我已将 'path tracing' 从 click 更改为 mouseover 事件，因此您可以在将鼠标悬停在节点上时看到效果。

一些值得注意的变化：

对于链接 d.source.id 和 d.target.id 分别变为 d.parent.id 和 d.id。
treeData 源数据定义只是一个对象而不是具有单个对象的数组
nodes 和 links 是用不同的方法创建的，但进入/更新/退出逻辑非常相似（除了上面的 source / parent 注释链接）

var treeData = {
  "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"
  }]
};

// ************** Generate the tree diagram  *****************
// Set the dimensions and margins of the diagram
var margin = {top: 20, right: 90, bottom: 30, left: 90},
    width = 960 - margin.left - margin.right,
    height = 180 - margin.top - margin.bottom;

// append the svg object to the body of the page
// appends a 'group' element to 'svg'
// moves the 'group' element to the top left margin
var svg = d3.select("body").append("svg")
    .attr("width", width + margin.right + margin.left)
    .attr("height", height + margin.top + margin.bottom)
  .append("g")
    .attr("transform", "translate("
          + margin.left + "," + margin.top + ")");

var i = 0,
    duration = 750,
    root;

// declares a tree layout and assigns the size
var treemap = d3.tree().size([height, width]);

// Assigns parent, children, height, depth
root = d3.hierarchy(treeData, function(d) { return d.children; });
root.x0 = height / 2;
root.y0 = 0;

update(root);

function update(source) {

  // Assigns the x and y position for the nodes
  var treeData = treemap(root);

  // Compute the new tree layout.
  var nodes = treeData.descendants(),
      links = treeData.descendants().slice(1);

  // 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 modes 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('mouseover', mouseover);

  // Add Circle for the nodes
  nodeEnter.append('circle')
      .attr('class', 'node')
    .attr("id", function(d){return "node" + d.id;})
      .attr('r', 1e-6)
      .style("fill", function(d) {
          return d._children ? "lightsteelblue" : "#fff";
      });

  // Add labels for the nodes
  nodeEnter.append('text')
      .attr("dy", ".35em")
      .attr("x", function(d) {
          return d.children || d._children ? -13 : 13;
      })
      .attr("text-anchor", function(d) {
          return d.children || d._children ? "end" : "start";
      })
      .text(function(d) { return d.data.name; });

  // UPDATE
  var nodeUpdate = nodeEnter.merge(node);

  // Transition to the proper position for the node
  nodeUpdate.transition()
    .duration(duration)
    .attr("transform", function(d) { 
        return "translate(" + d.y + "," + d.x + ")";
     });

  // Update the node attributes and style
  nodeUpdate.select('circle.node')
    .attr('r', 10)
    .style("fill", function(d) {
        return d._children ? "lightsteelblue" : "#fff";
    })
    .attr('cursor', 'pointer');


  // Remove any exiting nodes
  var nodeExit = node.exit().transition()
      .duration(duration)
      .attr("transform", function(d) {
          return "translate(" + source.y + "," + source.x + ")";
      })
      .remove();

  // On exit reduce the node circles size to 0
  nodeExit.select('circle')
    .attr('r', 1e-6);

  // On exit reduce the opacity of text labels
  nodeExit.select('text')
    .style('fill-opacity', 1e-6);
    
  // Update the links...
  var link = svg.selectAll('path.link')
      .data(links, function(d) { return d.id; });

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

  // UPDATE
  var linkUpdate = linkEnter.merge(link);

  // Transition back to the parent element position
  linkUpdate.transition()
      .duration(duration)
      .attr('d', function(d){ return diagonal(d, d.parent) });

  // Remove any exiting links
  var linkExit = link.exit().transition()
      .duration(duration)
      .attr('d', function(d) {
        var o = {x: source.x, y: source.y}
        return diagonal(o, 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 mouseover(event, d) {
  //reset all nodes color
  d3.selectAll("circle").style("fill", "white");
  d3.selectAll("path").style("stroke", "#c3c3c3");
  while (d.parent) {
    d3.selectAll("#node"+d.id).style("fill", "red")
    if (d.parent != "null")
      d3.selectAll("#link"+d.parent.id + "-" + d.id).style("stroke", "red")
    d = d.parent;
  }
}

// Creates a curved (diagonal) path from parent to the child nodes
function diagonal(s, d) {

  path = `M ${s.y} ${s.x}
          C ${(s.y + d.y) / 2} ${s.x},
            ${(s.y + d.y) / 2} ${d.x},
            ${d.y} ${d.x}`

  return path
}

.node {
  cursor: pointer;
}
.node circle {
  fill: #fff;
  stroke: steelblue;
  stroke-width: 3px;
}
.node text {
  font: 12px sans-serif;
}
.link {
  fill: none;
  stroke: #ccc;
  stroke-width: 2px;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/6.7.0/d3.min.js"></script>

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