Dynamic Labels: Add and Remove Data in v4 (sample dataset from Scott Murray's excellent book Interactive Data Visualization for the Web)

<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="utf-8">
		<title>Dynamic labels: Add and Remove data in v4 (sample dataset from Scott Murray's excellent book Interactive Data Visualization for the Web)</title>
		<script src="https://d3js.org/d3.v4.min.js"></script>
		<style type="text/css">

body {
		  font-family: Futura;
		  font-size: 16px;
			fill: white;
			background-color: white;

}

h1 {
			font-family: Futura;
			font-size: 24px;
			fill: white;
		}

</style>
	</head>
	<body>

<p id="add"	<h1>click me to add data</h1></p>
	<p id="remove"<h1>click me to remove data</h1></p>

var w = 600,
					h = 250,
					centered;

var dataset = [ { key: 0, value: 5 },
							{ key: 1, value: 10 },
							{ key: 2, value: 13 },
							{ key: 3, value: 19 },
							{ key: 4, value: 21 },
							{ key: 5, value: 25 },
							{ key: 6, value: 22 },
							{ key: 7, value: 18 },
							{ key: 8, value: 15 },
							{ key: 9, value: 13 },
							{ key: 10, value: 11 },
							{ key: 11, value: 12 },
							{ key: 12, value: 15 },
							{ key: 13, value: 20 },
							{ key: 14, value: 18 },
							{ key: 15, value: 17 },
							{ key: 16, value: 16 },
							{ key: 17, value: 18 },
							{ key: 18, value: 23 },
							{ key: 19, value: 25 } ];

var xScale = d3.scaleBand()
							.domain(d3.range(dataset.length))
							.rangeRound([0, w], 0.05);

var yScale = d3.scaleLinear()
							.domain([0, d3.max(dataset, function(d) { return d.value; })])
							.range([0, h]);

var key = function(d) {
				return d.key;
			};

var svg = d3.select("body")
						.append("svg")
						.attr("width", w)
						.attr("height", h);

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(10, 10, " + (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", "Futura")
			   .attr("font-size", "10px")
			   .attr("fill", "white");

d3.selectAll("p")
				.on("click", function() {

var paragraphID = d3.select(this).attr("id");

if (paragraphID == "add") {

var maxValue = 25;
						var newNumber = Math.floor(Math.random() * maxValue);
						var lastKeyValue = dataset[dataset.length - 1].key;
						console.log(lastKeyValue);
						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; })]);

var bars = svg.selectAll("rect")
						.data(dataset, key);

bars.enter()
						.append("rect")
						.attr("x", w)
						.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) + ")";
						});

bars.transition()
						.duration(500)
						.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);
						});

bars.exit()
						.transition()
						.ease(d3.easePoly)
						.duration(500)
						.attr("x", -xScale.bandwidth())
						.remove();

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

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", "Futura")
						.attr("font-size", "11px")
						.attr("fill", "white");

labels.transition()
						.duration(500)
						.ease(d3.easePoly)
						.attr("x", function(d, i) {
							return xScale(i) + xScale.bandwidth() / 2;
						});

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

});

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

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