Sorting bars in D3 from Chimera Labs copy

http://chimera.labs.oreilly.com/books/1230000000345/ch10.html#_click_to_sort

by Augustus Yuan

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.12/d3.min.js"></script>

	<body>
  </body>

CSS

rect:hover {
				fill: orange;
			}

JavaScript

//Width and height
			var w = 600;
			var h = 250;
			
			var dataset = [ 5, 10, 13, 19, 21, 25, 22, 18, 15, 13,
							11, 12, 15, 20, 18, 17, 16, 18, 23, 25 ];

			var xScale = d3.scale.ordinal()
							.domain(d3.range(dataset.length))
							.rangeRoundBands([0, w], 0.05);

			var yScale = d3.scale.linear()
							.domain([0, d3.max(dataset)])
							.range([0, h]);
			
			//Create SVG element
			var svg = d3.select("body")
						.append("svg")
						.attr("width", w)
						.attr("height", h);

			//Create bars
			svg.selectAll("rect")
			   .data(dataset)
			   .enter()
			   .append("rect")
			   .attr("x", function(d, i) {
			   		return xScale(i);
			   })
			   .attr("y", function(d) {
			   		return h - yScale(d);
			   })
			   .attr("width", xScale.rangeBand())
			   .attr("height", function(d) {
			   		return yScale(d);
			   })
			   .attr("fill", function(d) {
					return "rgb(0, 0, " + (d * 10) + ")";
			   })
			   .on("click", function() {
			   		sortBars();
			   });

			//Create labels
			svg.selectAll("text")
			   .data(dataset)
			   .enter()
			   .append("text")
			   .text(function(d) {
			   		return d;
			   })
			   .attr("text-anchor", "middle")
			   .attr("x", function(d, i) {
			   		return xScale(i) + xScale.rangeBand() / 2;
			   })
			   .attr("y", function(d) {
			   		return h - yScale(d) + 14;
			   })
			   .attr("font-family", "sans-serif")
			   .attr("font-size", "11px")
			   .attr("fill", "white");
			
			//Define sort order flag
			var sortOrder = false;
			
			//Define sort function
			var sortBars = function() {

				//Flip value of sortOrder
			   	sortOrder = !sortOrder;

				svg.selectAll("rect")
				   .sort(function(a, b) {
				   		if (sortOrder) {
					   		return d3.ascending(a, b);
				   		} else {
					   		return d3.descending(a, b);
				   		}
				   	})
				   .transition()
				   .delay(function(d, i) {
					   return i * 50;
				   })
				   .duration(1000)
				   .attr("x", function(d, i) {
				  ...