How to make nodes in sankey diagram clickable using d3.js library

Code Snippet :
We are using d3.js for this.
Sankey diagrams is made up of nodes and links.
Here the data comes from json file.
So how to make all the nodes clickable.
Which methods can we use with the rectangles so that we can make the nodes clickable.



<script>

var margin = {top: 1, right: 1, bottom: 6, left: 1},
width = 960 - margin.left - margin.right,
height = 500 - margin.top - margin.bottom;

var formatNumber = d3.format(",.0f"), //decimal places
format = function(d) { return formatNumber(d) + " TWh"; },
color = d3.scale.category20();

var svg = d3.select("#chart").append("svg")
.attr("width", width + margin.left + margin.right)
.attr("height", height + margin.top + margin.bottom)
.append("g")
.attr("transform", "translate(" + margin.left + "," + margin.top + ")");

var sankey = d3.sankey()
.nodeWidth(15)
.nodePadding(10)
.size([width, height]);

var path = sankey.link();

//d3.json("energy.json", function(energy) {


d3.json("numbers-subset.json", function(energy) {



sankey
.nodes(energy.nodes)
.links(energy.links)
.layout(32);

var link = svg.append("g").selectAll(".link")
.data(energy.links)
.enter().append("path")
.attr("class", "link")
.attr("d", path)
.style("stroke-width", function(d) { return Math.max(1, d.dy); })
.sort(function(a, b) { return b.dy - a.dy; });


link.append("title")
.text(function(d) { return d.source.name + " → " + d.target.name + "\n" + format(d.value); });


var node = svg.append("g").selectAll(".node")
.data(energy.nodes)
.enter().append("g")
.attr("class", "node")
.attr("transform", function(d) { return "translate(" + d.x + "," + d.y + ")"; })
.call(d3.behavior.drag()
.origin(function(d) { return d; })
.on("dragstart", function() { this.parentNode.appendChild(this); })
.on("drag", dragmove));

node.append("rect")
.attr("height", function(d) { return d.dy; })
.attr("width", sankey.nodeWidth())
.style("fill", function(d) { return d.color = color(d.name.split("|")[0]); })
.style("stroke", function(d) { return d3.rgb(d.color).darker(2); })
.append("title")
.text(function(d) { return d.name + "\n" + format(d.value); });

node.append("text")
.attr("x", -6)
.attr("y", function(d) { return d.dy / 2; })
.attr("dy", ".35em")
.attr("text-anchor", "end")
.attr("transform", null)
.text(function(d) { return d.name; })
.filter(function(d) { return d.x < width / 2; })
.attr("x", 6 + sankey.nodeWidth())
.attr("text-anchor", "start");

function dragmove(d) {
d3.select(this).attr("transform", "translate(" + d.x + "," + (d.y = Math.max(0, Math.min(height - d.dy, d3.event.y))) + ")");
sankey.relayout();
link.attr("d", path);
}



});

</script>