Dynamic bar widths

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  </style>
</head>

<body>
  <script>
    // *** Add or remove integer data items from this array to see dynamic bar width
    var data = [1,2,4,5,3,4,7,4,2,2,5];
    var svgwidth = 960;
    
    // *** Calculate bar width to fill svg widthways
    var barwidth = (svgwidth/data.length) * 0.5;
    var barpadding = (svgwidth/data.length) * 0.5;
    
    
    var svg = d3.select("body").append("svg")
      .attr("width", svgwidth)
      .attr("height", 500)
    
    var rects = svg.selectAll("rect").data(data);

rects.enter().append("rect")
      .attr("y", calcy)
      .attr("x", calcx)
    	.attr("width", barwidth)
    	.attr("height", calcheight)
    	.attr("fill", "black");
    
    function calcx(d, i){
      return i * (barwidth + barpadding) + (barpadding/2);
    }
    
    function calcy(d){
      return 200 - calcheight(d);
    }
    
    function calcheight(d){
			return d * 20;
    }

</script>
</body>

https://d3js.org/d3.v4.min.js