Band scale

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3-array.v0.7.min.js"></script>
  <script src="https://d3js.org/d3-collection.v0.1.min.js"></script>
  <script src="https://d3js.org/d3-color.v0.4.min.js"></script>
  <script src="https://d3js.org/d3-format.v0.5.min.js"></script>
  <script src="https://d3js.org/d3-interpolate.v0.5.min.js"></script>
  <script src="https://d3js.org/d3-scale.v0.6.min.js"></script>
  
  <script src="https://d3js.org/d3-selection.v0.6.min.js"></script>
  <script src="https://d3js.org/d3-axis.v0.2.min.js"></script>
  
  <script src="https://d3js.org/d3-array.v0.6.min.js"></script>
  <style>
    line, path, .domain, .bar {
      stroke: black;
      fill: none;
    }
    text{
      fill: black;
    }
    
  </style>
</head>
<body>
  <script>
    var margin = {top: 20, right: 10, bottom: 40, left: 10};
    var width = 500;
    var height = 400;
    var chartWidth = 500 - margin.left - margin.right;
    var chartHeight = 400 - margin.top - margin.bottom;
    var axisHeight = 30;
    var data = [
      {key:'A', value: 1},
      {key:'B', value: 3},
      {key:'C', value: 2},
      {key:'D', value: 3},
      {key:'E', value: 4},
    ];
    
		var scaleX = d3_scale.scaleBand()
    	.domain(data.map(function(d){ return d.key; }))
    	.range([0, chartWidth])
    	.paddingInner([0.1])
	    .paddingOuter([0.3])
	    .align([0.5]);
    
    var scaleY = d3_scale.scaleLinear()
      .domain([0, d3_array.max(data.map(function(d){ return d.value; }))])
      .range([0, chartHeight]);
    
    var axis = d3_axis.axisBottom(scaleX)
	    .tickSizeInner(4)
    	.tickSizeOuter(20)
	    .tickPadding(3);
    
    var panel = d3_selection.select("body").append("svg")
      .attr("class", "axis")
      .attr("width", width)
      .attr("height", height)
     .append("g")
      .attr("transform", "translate("+[margin.left, margin.top]+")")
    
    panel.attr("transform", "translate("+[margin.left, height - margin.bottom]+")")
      .call(axis);
    
    panel.selectAll('rect.bar')
    	.data(data)
    	.enter().append('rect')
    	.attr("class", "bar")
	    .attr("width", scaleX.bandwidth())
    	.attr("height", function(d){ return scaleY(d.value); })
	    .attr("x", function(d){ return scaleX(d.key); })
	    .attr("y", function(d){ return -scaleY(d.value); })
    
  </script>
</body>

https://d3js.org/d3-array.v0.7.min.js

https://d3js.org/d3-collection.v0.1.min.js

https://d3js.org/d3-color.v0.4.min.js

https://d3js.org/d3-format.v0.5.min.js

https://d3js.org/d3-interpolate.v0.5.min.js

https://d3js.org/d3-scale.v0.6.min.js

https://d3js.org/d3-selection.v0.6.min.js

https://d3js.org/d3-axis.v0.2.min.js

https://d3js.org/d3-array.v0.6.min.js