How to add different class name to each level in d3.js

Question

I trying to add different class name for each level without using json values

// Generate class string
  function getCircleClasses(d)
  {
    var classes = "node-L00";
    if (d.parent)
    {
      classes = "node-L";  
    }
    if (d.children)
    {
      classes += " emphasis"; 
    }

    return classes;
  }

Answer 1

Use classed routine of D3:

...
  .selectAll('circle.node')
  .data(data)
  .enter()
  .append('circle')
  .classed('node', true)
  .classed('has-parent', d => d.parent)
  .classed('has-children', d => d.children?.length > 0)