Appended text not appearing when using D3

Question

I'm trying to get this text to display on mouseover but it's not working, can anyone give some insights? There are multiple circles in the document and I want each one to display overhead text on mouseover. Current form should be displaying "hello"s everywhere but there's nothing.

  d3.selectAll("circle")
    .on("mouseover",function(d){

    var x = parseFloat( d3.select(this).attr("cx") );
    var y = parseFloat( d3.select(this).attr("cy") );

    d3.selectAll("circle")
       .append("text")
       .attr("class","tooltipText")
       .attr("x",x)
       .attr("y",y)
       .attr("stroke-width",1)
       .attr("fill", "white")
       .attr("font-size", "13px")
       .attr("text-anchor", "middle")

       .text(function(){

          return "hello";

       });

    });

Answer 1

You should encapsulate your circles inside of g elements. These will act as <div> tags in HTML. You can add a class attribute to these elements so they will be easily selected afterwards.

//circles creation
var circles = d3.selectAll('svg').append('svg')
              .append('g').attr('class', 'circles').data( someData );

circles.enter().append('g').attr('class', 'circle')
               .append('circle')
                 .attr('cx', function(d) { return xScale(d); })
                 .attr('cy', function(d) { return yScale(d); })
               .append('text').attr('style', 'display:none;')
                 .text(function(d) { return d.title; })
                 .attr('x', function(d) { return xScale(d); })
                 .attr('y', function(d) { return yScale(d) + 2*radius(d); });

d3.selectAll('.circle').on('mouseover', function( data, index, element ) {
    d3.select( element ).attr('style', '');
});

Notice that xScale, yScale, radius are all function of the data.