Bezier Curves with Text

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  </style>
</head>

<body>
  <script>
    var width = 600, height = 400, opacity = 0.5;
    var cubicPath = "M20,20 C300,200 100,500 400,100";
    var quadPath = "M200,20 Q100,300 500,100";
    var cValues = "M20,20 C300,200 100,500 400,100";
    var qValues = "M200,20 Q100,300 500,100";
    var fontSizeC = "24";
    var fontSizeQ = "18";
    var textC = "follows the curve from one side";
    var textQ = "follows the curve from the other side";
    var fillColors = ["red", "blue", "green", "yellow"];
    
    //svg container
    var svgContainer = d3.select("body").append("svg")
    .attr("width", width)
    .attr("height", height);
    
    var defs = svgContainer.append("svg:defs");
    
    var patternC = defs.append("svg:path")
    .attr("id", "pathInfoC")
    .attr("d", cValues);
    
    var patternQ = defs.append("svg:path")
    .attr("id", "pathInfoQ")
    .attr("d", qValues);
    
    //now add the 'g' element
    var g1 = svgContainer.append("svg:g");
    
    //create the cubic curve
    var bezierC = g1.append("path")
    .attr("d", cubicPath)
    .attr("fill", fillColors[0])
    .attr("stroke", "blue")
    .attr("stroke-width", 2);
    
    //text for the cubic
    var textC = g1.append("text")
    .attr("id", "textStyleC")
    .attr("stroke", "blue")
    .attr("fill", fillColors[1])
    .attr("stroke-width", 2)
    	.append("textPath")
    	.attr("font-size", fontSizeC)
    	.attr("xlink:href", "#pathInfoC")
    	.text(textC);
    
    //create the quadratic curve
    var bezierQ = g1.append("path")
    .attr("d", quadPath)
    .attr("fill", fillColors[1])
    .attr("opacity", opacity)
    .attr("stroke", "blue")
    .attr("stroke-width", 2);
    
    //text for the quad curve
    var textQ = g1.append("text")
    .attr("id", "textStyleQ")
    .attr("stroke", fillColors[3])
    .attr("stroke-width", 2)
    	.append("textPath")
    	.attr("font-size", fontSizeQ)
    	.attr("xlink:href", "#pathInfoQ")
    	.text(textQ);
  </script>
</body>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js