ashayh/index.html

## index.html
<!DOCTYPE html>
<meta charset="UTF-8">
<style>

.node circle {
  fill: #fff;
  stroke: steelblue;
  stroke-width: 3px;
}

.node text {
  font: 12px sans-serif;
}

.link {
  fill: none;
  stroke: #ccc;
  stroke-width: 2px;
}

</style>

<body>

<!-- load the d3.js library -->
<script src="https://d3js.org/d3.v5.min.js"></script>
<script>

var treeData =
  {
    "name": "Top Level",
    "children": [
      {
        "name": "Level 2: A",
        "children": [
          { "name": "Son of A" },
          { "name": "Daughter of A" }
        ]
      },
      { "name": "Level 2: B" }
    ]
  };

// Set the dimensions and margins of the diagram
var margin = {top: 40, right: 120, bottom: 20, left: 120},
    width = 960 - margin.left - margin.right,
    height = 500 - 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;

// Collapse after the second level
root.children.forEach(collapse);

update(root);

// Collapse the node and all it's children
function collapse(d) {
  if(d.children) {
    d._children = d.children
    d._children.forEach(collapse)
    d.children = null
  }
}

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});

  // ****************** Nodes section ***************************

  // 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('click', click);

  // Add Circle for the nodes
  nodeEnter.append('circle')
      .attr('class', 'node')
      .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);

  // ****************** links section ***************************

  // 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('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();

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

  // 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
  }

  // 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);
  }
}

</script>
</body>
	<!DOCTYPE html>
	<meta charset="UTF-8">
	<style>

	.node circle {
	fill: #fff;
	stroke: steelblue;
	stroke-width: 3px;
	}

	.node text {
	font: 12px sans-serif;
	}

	.link {
	fill: none;
	stroke: #ccc;
	stroke-width: 2px;
	}

	</style>

	<body>

	<!-- load the d3.js library -->
	<script src="https://d3js.org/d3.v5.min.js"></script>
	<script>

	var treeData =
	{
	"name": "Top Level",
	"children": [
	{
	"name": "Level 2: A",
	"children": [
	{ "name": "Son of A" },
	{ "name": "Daughter of A" }
	]
	},
	{ "name": "Level 2: B" }
	]
	};

	// Set the dimensions and margins of the diagram
	var margin = {top: 40, right: 120, bottom: 20, left: 120},
	width = 960 - margin.left - margin.right,
	height = 500 - 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;

	// Collapse after the second level
	root.children.forEach(collapse);

	update(root);

	// Collapse the node and all it's children
	function collapse(d) {
	if(d.children) {
	d._children = d.children
	d._children.forEach(collapse)
	d.children = null
	}
	}

	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});

	// **************** Nodes section *************************

	// 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('click', click);

	// Add Circle for the nodes
	nodeEnter.append('circle')
	.attr('class', 'node')
	.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);

	// **************** links section *************************

	// 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('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();

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

	// 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
	}

	// 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);
	}
	}

	</script>
	</body>