D3 Slider by curran

index.html

<!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;
      padding: 0;
    }
  </style>
</head>
<body>
  <script>
    var width = 960;
    var height = 500;
    var radius = 20;
    var margin = 100;
    
    var x1 = margin;
    var x2 = width - margin;
    var y = height / 2;
        
    var drag = d3.behavior.drag()
      .origin(function(d) { return d; })
      .on("drag", dragmove);
    
    var svg = d3.select("body").append("svg")
      .attr("width", width)
      .attr("height", height)
      .datum({
        x: width / 2,
        y: height / 2
      });
    
    var line = svg.append("line")
      .attr("x1", x1)
      .attr("x2", x2)
      .attr("y1", y)
      .attr("y2", y)
      .style("stroke", "black")
      .style("stroke-linecap", "round")
      .style("stroke-width", 5);

    var circle = svg.append("circle")
      .attr("r", radius)
      .attr("cy", function(d) { return d.y; })
      .attr("cx", function(d) { return d.x; })
      .style("cursor", "ew-resize")
      .call(drag);
    
    function dragmove(d) {
      
      // Get the updated X location computed by the drag behavior.
      var x = d3.event.x;
      
      // Constrain x to be between x1 and x2 (the ends of the line).
      x = x < x1 ? x1 : x > x2 ? x2 : x;
      
      // This assignment is necessary for multiple drag gestures.
      // It makes the drag.origin function yield the correct value.
      d.x = x;
      
      // Update the circle location.
      circle.attr("cx", x);
    }
  </script>
</body>