Placing labels at the center of nodes in d3.js

The text-anchor attribute works as expected on an svg element created by D3. However, you need to append the text and the circle into a common g element to ensure that the text and the circle are centered with one another.

To do this, you can change your nodes variable to:

var nodes = svg.append("g")
           .attr("class", "nodes")
           .selectAll("circle")
           .data(dataset)
           .enter()
           // Add one g element for each data node here.
           .append("g")
           // Position the g element like the circle element used to be.
           .attr("transform", function(d, i) {
             // Set d.x and d.y here so that other elements can use it. d is 
             // expected to be an object here.
             d.x = i * 70 + 50,
             d.y = svg_h / 2;
             return "translate(" + d.x + "," + d.y + ")"; 
           });

Note that the dataset is now a list of objects so that d.y and d.x can be used instead of just a list of strings.

Then, replace your circle and text append code with the following:

// Add a circle element to the previously added g element.
nodes.append("circle")
      .attr("class", "node")
      .attr("r", 20);

// Add a text element to the previously added g element.
nodes.append("text")
     .attr("text-anchor", "middle")
     .text(function(d) {
       return d.name;
      });

Now, instead of changing the position of the circle you change the position of the g element which moves both the circle and the text.

Here is a JSFiddle showing centered text on circles.

If you want to have your text be in a separate g element so that it always appears on top, then use the d.x and d.y values set in the first g element’s creation to transform the text.

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

text.append("svg:text")
    .attr("text-anchor", "middle")
    .text(function(d) { return d.name; });

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