Unable to get click event in D3 JavaScript library

Question

I am using D3 JavaScript library to display data as a force directed marker. It works fine. But I am unable to add click event to the circle. so when I click on the circle, I get detailed analysis of the circle and display it in a modal box.

var links = [{source: "x", target:"y", type: "paid"},......]';

var nodes = {};

// Compute the distinct nodes from the links.
links.forEach(function(link) {
  link.source = nodes[link.source] || (nodes[link.source] = {name: link.source});
  link.target = nodes[link.target] || (nodes[link.target] = {name: link.target});
});

var w = 950,
    h = 500;

var force = d3.layout.force()
    .nodes(d3.values(nodes))
    .links(links)
    .size([w, h])
    .linkDistance(60)
    .charge(-300)
    .on("tick", tick)
    .start();

var svg = d3.select("#graph").append("svg:svg")
    .attr("width", w)
    .attr("height", h);

// Per-type markers, as they don't inherit styles.
svg.append("svg:defs").selectAll("marker")
    .data(["suit", "licensing", "resolved"])
  .enter().append("svg:marker")
    .attr("id", String)
    .attr("viewBox", "0 -5 10 10")
    .attr("refX", 15)
    .attr("refY", -1.5)
    .attr("markerWidth", 6)
    .attr("markerHeight", 6)
    .attr("orient", "auto")
    .append("svg:path")
    .attr("d", "M0,-5L10,0L0,5");

var path = svg.append("svg:g").selectAll("path")
    .data(force.links())
  .enter().append("svg:path")
    .attr("class", function(d) { return "link " + d.type; })
    .attr("marker-end", function(d) { return "url(#" + d.type + ")"; });

var circle = svg.append("svg:g").selectAll("circle")
    .data(force.nodes())
    .enter().append("svg:circle")
    .attr("r", 6)
    .call(force.drag);

var text = svg.append("svg:g").selectAll("g")
    .data(force.nodes())
    .enter().append("svg:g");

// A copy of the text with a thick white stroke for legibility.
text.append("svg:text")
    .attr("x", 8)
    .attr("y", ".31em")
    .attr("class", "shadow")
    .text(function(d) { return d.name; });

text.append("svg:text")
    .attr("x", 8)
    .attr("y", ".31em")
    .text(function(d) { return d.name; });

// Use elliptical arc path segments to doubly-encode directionality.
function tick() {
  path.attr("d", function(d) {
    var dx = d.target.x - d.source.x,
        dy = d.target.y - d.source.y,
        dr = Math.sqrt(dx * dx + dy * dy);
    return "M" + d.source.x + "," + d.source.y + "A" + dr + "," + dr + " 0 0,1 " + d.target.x + "," + d.target.y;
  });

  circle.attr("transform", function(d) {
    return "translate(" + d.x + "," + d.y + ")";
  });

  text.attr("transform", function(d) {
    return "translate(" + d.x + "," + d.y + ")";
  });
}

I tried adding .on("click", 'alert(\'Hello world\')') to var circle. It does not work as expected. It alerts on load instead on click.

I appreciate any help

Answer 1

Try this:

var circle = svg.append("svg:g").selectAll("circle")
  .data(force.nodes())
  .enter().append("svg:circle")
  .attr("r", 6)
  .on("click", function(d,i) { alert("Hello world"); })
  .call(force.drag);

Answer 2

Try out this, if you want the node contained within the circle (let's say that your nodes are mapping an object with a key called anger and a value 34:

var circle = svg.append("svg:g").selectAll("circle")
.data(force.nodes())
.enter().append("svg:circle")
.attr("r", 6)
.on("click", function(d,i) { alert(d.anger); }) // this will alert 34
.call(force.drag);

Or try this for the attributes of the svg (getting the radius of the svg, for example):

var circle = svg.append("svg:g").selectAll("circle")
.data(force.nodes())
.enter().append("svg:circle")
.attr("r", 6)
.on("click", function(d,i) { alert(d3.select(this).r; }) // this will print out the radius })
.call(force.drag);

Sorry if my post is like the one above, but I thought the clarification could be useful.