// ### DATA MODEL START

var data = {
	type: 'action',
  name: '1',
  attributes: [],
  children: [{
  	type: 'children',
  	name: '2',
    attributes: [{
    	'source-type-property-value': 'streetlight'
    }],
    children: [{
    	type: 'parents',
  		name: '3',
      attributes: [{
      	'source-type-property-value': 'cable'
      }],
      children: [{
      	type: 'resource-delete',
  			name: '4',
        attributes: [],
        children: []
      }]
    }, {
    	type: 'children',
  		name: '5',
      attributes: [{
      	'source-type-property-value': 'lantern'
      }],
      children: []
    }]
  }]
};

// ### DATA MODEL END

// 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 = 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(data, function(d) {
	return d.children;
});
root.x0 = height / 2;
root.y0 = 0;

update(root);

var selected = 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
  });

  // ### LINKS

  // Update the links...
  var link = svg.selectAll('line.link').
  	data(links, function(d) {
    	return d.id;
    });

  // Enter any new links at the parent's previous position.
  var linkEnter = link.enter().
  	append('line').
    attr("class", "link").
    attr("stroke-width", 2).
    attr("stroke", 'black').
    attr('x1', function(d) {
    	return source.y0;
    }).
    attr('y1', function(d) {
    	return source.x0;
    }).
    attr('x2', function(d) {
    	return source.y0;
    }).
    attr('y2', function(d) {
    	return source.x0;
    });
    
  var linkUpdate = linkEnter.merge(link);
  
  linkUpdate.transition().
  	duration(duration).
    attr('x1', function(d) {
    	return d.parent.y;
    }).
    attr('y1', function(d) {
    	return d.parent.x;
    }).
    attr('x2', function(d) {
    	return d.y;
    }).
    attr('y2', function(d) {
    	return d.x;
    });

  // Transition back to the parent element position
  linkUpdate.transition().
  	duration(duration).
    attr('x1', function(d) {
    	return d.parent.y;
    }).
    attr('y1', function(d) {
    	return d.parent.x;
    }).
    attr('x2', function(d) {
    	return d.y;
    }).
    attr('y2', function(d) {
    	return d.x;
    });

  // Remove any exiting links
  var linkExit = link.exit().
  	transition().
    duration(duration).
    attr('x1', function(d) {
    	return source.x;
    }).
    attr('y1', function(d) {
    	return source.y;
    }).
    attr('x2', function(d) {
    	return source.x;
    }).
    attr('y2', function(d) {
    	return source.y;
    }).
    remove();

	// ### CIRCLES

  // 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', 25).
    style("fill", function(d) {
    	return "#0e4677";
    });

  // 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', 25).
    style("fill", function(d) {
    	return "#0e4677";
  	}).
    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', 0);
  
  // Store the old positions for transition.
  nodes.forEach(function(d){
    d.x0 = d.x;
    d.y0 = d.y;
  });

  // Toggle children on click.
  function click(d) {
    selected = d;
    document.getElementById('add-child').disabled = false;
    document.getElementById('remove').disabled = false;
    update(d);
  }
}

document.getElementById('add-child').onclick = function() {
  
  //creates New OBJECT
  var newNodeObj = {
  	type: 'resource-delete',
    name: new Date().getTime(),
    attributes: [],
    children: []
  };
  //Creates new Node 
  var newNode = d3.hierarchy(newNodeObj);
  newNode.depth = selected.depth + 1; 
  newNode.height = selected.height - 1;
  newNode.parent = selected; 
  newNode.id = Date.now();
  
  if(!selected.children){
    selected.children = [];
  	    selected.data.children = [];
  }
  selected.children.push(newNode);
  selected.data.children.push(newNode.data);
  
  update(selected);
};

<script src="https://d3js.org/d3.v4.min.js"></script>
<button id="add-child" disabled="disabled">Add Child</button>