D3 - Enter Selection

<!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; }
 
    #chart {
      margin: 3em;
    }
    .bar {
      background-color: blue;
  		height: 20px;
  		margin-top: 2px;
    }
  </style>
</head>

<body>
  
  <svg id="chart"></svg>
  
  <script>
    var rectWidth = 50;
    var chartHeight = 400;
    var chartWidth = 700;
    
    var data = [200, 60, 100, 80, 10];

</script>
</body>

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