reusable tree

<!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>
  <div id="weatherHistory"></div>
  <div id="runningHistory"</div>
  <script>
    // Using Mike Bostock's Towards Reusable Charts Pattern
	function barChart() {
 
    	// All options that should be accessible to caller
    	var width = 900;
    	var height = 200;
    	var barPadding = 1;
    	var fillColor = 'steelblue';
 
    	function chart(selection){
            selection.each(function (data) {
            	var barSpacing = height / data.length;
            	var barHeight = barSpacing - barPadding;
            	var maxValue = d3.max(data);
            	var widthScale = width / maxValue;
 
                d3.select(this).append('svg')
                    .attr('height', height)
                    .attr('width', width)
                    .selectAll('rect')
                    .data(data)
                	.enter()
                    .append('rect')
                    .attr('y', function (d, i) { return i * barSpacing })
                    .attr('height', barHeight)
                    .attr('x', 0)
                    .attr('width', function (d) { return d*widthScale})
                    .style('fill', fillColor);
        	});
    	}
 
    	chart.width = function(value) {
        	if (!arguments.length) return margin;
        	width = value;
        	return chart;
    	};
 
    	chart.height = function(value) {
        	if (!arguments.length) return height;
        	height = value;
        	return chart;
    	};
 
        chart.barPadding = function(value) {
        	if (!arguments.length) return barPadding;
        	barPadding = value;
        	return chart;
    	};
 
        chart.fillColor = function(value) {
        	if (!arguments.length) return fillColor;
        	fillColor = value;
        	return chart;
    	};
 
    	return chart;
	}	
	var milesRun = [2, 5, 4, 1, 2, 6, 5];
	var highTemperatures = [77, 71, 82, 87, 84, 78, 80, 84, 86, 72, 71, 68, 75, 73, 80, 85, 86, 80];
 
	var runningChart = barChart().barPadding(2);
    d3.select('#runningHistory')
            .datum(milesRun)
            .call(runningChart);
 
	var weatherChart = barChart().fillColor('coral');
    d3.select('#weatherHistory')
            .datum(highTemperatures)
            .call(weatherChart);

</script>
</body>

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