Bar charts (add and remove)

<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="utf-8">
		<title>D3: Adding and removing values from a chart (dynamic labels included)</title>
		<script src="https://d3js.org/d3.v5.min.js"></script>
		<style type="text/css">
		</style>
	</head>
	<body>
	
		<p id="add">Add new value</p>
		<p id="remove">Remove value</p>
			
		<script type="text/javascript">

svg.selectAll("rect")
			   .data(dataset, key)
			   .enter()
			   .append("rect")
			   .attr("x", function(d, i) {
			   		return xScale(i);
			   })
			   .attr("y", function(d) {
			   		return h - yScale(d.value);
			   })
			   .attr("width", xScale.bandwidth())
			   .attr("height", function(d) {
			   		return yScale(d.value);
			   })
			   .attr("fill", function(d) {
					return "rgb(0, 0, " + (d.value * 10) + ")";
			   });

svg.selectAll("text")
			   .data(dataset, key)
			   .enter()
			   .append("text")
			   .text(function(d) {
			   		return d.value;
			   })
			   .attr("text-anchor", "middle")
			   .attr("x", function(d, i) {
			   		return xScale(i) + xScale.bandwidth() / 2;
			   })
			   .attr("y", function(d) {
			   		return h - yScale(d.value) + 14;
			   })
			   .attr("font-family", "sans-serif")
			   .attr("font-size", "11px")
			   .attr("fill", "white");
            
    			d3.selectAll("p")
				.on("click", function() {
					var paragraphID = d3.select(this).attr("id");
                    if (paragraphID == "add") {
						var minValue = 2;
						var maxValue = 25 - minValue;
						var newNumber = Math.floor(Math.random() * maxValue) + minValue;
						var lastKeyValue = dataset[dataset.length - 1].key;
						dataset.push({
							key: lastKeyValue + 1,
							value: newNumber
						});
					} else {
						dataset.shift();	
					} 
					
					xScale.domain(d3.range(dataset.length));
					yScale.domain([0, d3.max(dataset, function(d) { return d.value; })]);

bars.exit()
						.transition()
						.duration(500)
						.attr("x", -xScale.bandwidth())
						.remove();

var labels = svg.selectAll("text")
						.data(dataset, key);

labels.exit()
  						.transition()
  						.duration(500)
  						.attr("x", -xScale.bandwidth())
  						.remove();
					
					labels.enter()
						.append("text")
						.text(function(d) {
							return d.value;
						})
						.attr("text-anchor", "middle")
						.attr("x", w)
						.attr("y", function(d) {
							return h - yScale(d.value) + 14;
						})						
					   .attr("font-family", "sans-serif")
					   .attr("font-size", "11px")
					   .attr("fill", "white")
					   .merge(labels)	//Update…
					   .transition()
					   .duration(500)
					   .attr("x", function(d, i) {
							return xScale(i) + xScale.bandwidth() / 2;
					   });

});

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

https://d3js.org/d3.v5.min.js