title: .on ('mouseover') on d3
body: <p>I have a clarification question regarding the .on('mouseover') method in d3.
  The code I have is:</p>
  
  <pre><code>svg.selectAll('text')
              .data(dataset)
              .enter()
              .append('text')
              .attr('x',function(d){
                return xScale(d[0]);
              })
              .attr('y',function(d){
                return yScale(d[1]);
              })
              .text(function(d) {
                  return d[0] + ',' + d[1];
                })
              .style('visibility','hidden');
              .on('mouseover',...)
  </code></pre>
  
  <p>What kind of function shall I put instead of the <code>...</code> in the code to make the style of a single text tag become <code>visible</code> when hovering with the mouse?</p>
  
  <p>I have checked different solutions but none of them work.
  (One is: <a href="https://stackoverflow.com/questions/18991680/d3-trigger-mouseover-event">d3 - trigger mouseover event</a>)</p>
  
  <p>Moreover, I was wondering if what I thought about d3 workflow is corrected (I started to learn d3 only yesterday so be patient..):
  <code>.selectAll</code> iterates through what it is given to it inside the <code>.data</code> argument.
  At each iteration a text object(?) is created at the given position and with a given label. What does the <code>.style</code> refer to? The single object <code>.selectAll</code> iterates through? So are there multiple <code>.style</code> for each object iterated? And how to modify that object? Would <code>d3.select(this).style('visibility','visible')</code> be enough? (Looking at the link above it does not seem so...)</p>