23. CSS hover vs mouseover-mouseout-transition

<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="utf-8">
		<title>D3: Sorting and re-sorting visual elements with delay</title>
    
		<script type="text/javascript" src="https://d3js.org/d3.v4.min.js"></script>
    
		<style type="text/css">

rect:hover {
				fill: orange;
			}

</style>
    
	</head>
  
	<body>
		<script type="text/javascript">

var w = 600;
			var h = 250,
          margin = {top: 20, bottom:20, left:30, right:40},
          width = w - margin.right - margin.left,
          height = h - margin.top - margin.bottom;
			
      
      var svg = d3.select("body")
      .append("svg")
      .attr("width", w)
      .attr("height", h)
      .append("g")
      .attr("transform", "translate("+margin.left+","+margin.top+")");
      
      
			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.scaleBand()
							.domain(d3.range(dataset.length))
							.rangeRound([0, width])
      				.padding(0.05);

var yScale = d3.scaleLinear()
							.domain([0, d3.max(dataset)])
							.range([height, 0]);

svg.selectAll("rect")
			   .data(dataset)
			   .enter()
			   .append("rect")
			   .attr("x", function(d, i) {
			   		return xScale(i);
			   })
			   .attr("y", function(d) {
			   		return yScale(d);
			   })
			   .attr("width", xScale.bandwidth())
			   .attr("height", function(d) {
			   		return height - yScale(d);
			   })
			   .attr("fill", function(d) {
					return "rgb(0, 0, " + (d * 10) + ")";
			   })
			   .on("click", function() {
			   		sortBars();
			   })
      
// ---- during click transition, if mouse transition occurs, click transition will be disrupted. 
//       Solution: to use CSS hover replace mouseover and mouseout transition
//       Drawbacks: losing fade effect => duration(250)
      
// ---- event listener: .on("mouseover", function(){})      
// 			   .on("mouseover", function() {
// 			   		d3.select(this)
// 			   			.attr("fill", "orange");
// 			   })
           
// 			   .on("mouseout", function(d) {
// 				   d3.select(this)
// 				   		.transition()
// 				   		.duration(250)
// 						.attr("fill", "rgb(0, 0, " + (d * 10) + ")");
// 			   });

;

//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.bandwidth() / 2;
			   })
			   .attr("y", function(d) {
			   		return 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) {
				   		return xScale(i);
				   });
        
        svg.selectAll("text")
				   .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) {
				   		return xScale(i) + xScale.bandwidth()/2;
				   });

};

</script>
	</body>
</html>

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