You are adding a text element inside a circle, that won't work. You can add groups under the svg element and then append the circle and a text in each group:
// Create the groups under svg
var gnodes = svg.selectAll('g.gnode')
.data(graph.nodes)
.enter()
.append('g')
.classed('gnode', true);
// Add one circle in each group
var node = gnodes.append("circle")
.attr("class", "node")
.attr("r", 5)
.style("fill", function(d) { return color(d.group); })
.call(force.drag);
// Append the labels to each group
var labels = gnodes.append("text")
.text(function(d) { return d.name; });
force.on("tick", function() {
// Update the links
link.attr("x1", function(d) { return d.source.x; })
.attr("y1", function(d) { return d.source.y; })
.attr("x2", function(d) { return d.target.x; })
.attr("y2", function(d) { return d.target.y; });
// Translate the groups
gnodes.attr("transform", function(d) {
return 'translate(' + [d.x, d.y] + ')';
});
});
A fork of your fiddle with this strategy is here
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