Health & Wealth full animation

<!DOCTYPE html>
<head>
	<script src="https://d3js.org/d3.v4.min.js"></script>

.axis {
			font-family: "Courier";
			font-size: 20px;
			fill: #000;
		}

.circle {
			fill-opacity: .9;
			stroke: #000;
		}

.domain {
			stroke: #000;
		}

.tick > line {
			stroke: #000;
		}

.year {
			font-family: "Courier";
			font-size: 50px;
			fill: #000;
		}
	</style>
</head>
<body>
	<script>
		var scales = {};
		var year = 1950;

var filterByYear = function(input, year) {
			var result = [];

input.forEach(function(i) {
				var country = {
					year: null,
					country: null,
					region: null,
					income: null,
					lifeExpectancy: null,
					population: null
				}

var getIncome = getAttrByYear(i, country, year, "income");
				var getLifeExpectancy = getAttrByYear(i, country, year, "lifeExpectancy");
				var getPopulation = getAttrByYear(i, country, year, "population");
				country.country = i.name;
				country.region = i.region;
				country.year = year;
				result.push(country);
			});

return result;
		};

var getAttrByYear = function(input, output, year, attr) {
			input[attr].forEach(function(d) { 
				if (d[0] === year) { 
					return output[attr] = d[1];
				}
			});
		};

return [min, max];
		};

var update = function(data, svg, scales, year) {
			var newData = filterByYear(data, year);

var selection = svg.selectAll("circle")
				.data(newData);

selection.enter()
				.append("circle")
				.merge(selection)
				.transition()
				.attr("cx", function(d) { 
					if (d.income != null) {
						return scales.xSca(d.income)
				}})
				.attr("cy", function(d) {
					if (d.lifeExpectancy != null) {
						return scales.ySca(d.lifeExpectancy)
					}
				})
				.attr("r", function(d) {
					if ((d.income && d.lifeExpectancy && d.population) != null) {
						return scales.rSca(d.population) 
					}
				})
				.attr("id", function(d) { return d.country })
				.attr("fill", function(d) { return scales.cSca(d.region) })
				.attr("class", "circle");

selection.select('text')
      	.attr('x', function(d) { 
					if (d.income != null) {
						return scales.xSca(d.income)
				}})
      	.attr('y', function(d) {
					if (d.lifeExpectancy != null) {
						return scales.ySca(d.lifeExpectancy)
					}
				})
      	.text(function(d) { return d.key })
      
			d3.select(".year").text(year);
			
			selection.exit().remove();
		};
		
		d3.json("nations.json", function(error, data) {
			if (error) return error;
			console.log(data);		// original data

// data
			// var year = 1950;
			newData = filterByYear(data, year);
			console.log(newData);	// filtered data

// vars -----------------------------------------------------------

var margin = { top: 20, right: 20, bottom: 20, left: 20 };
			var width = 960 - margin.left - margin.right;
			var height = 500 - margin.top - margin.bottom;

// min-max
			var xExtent = getMinMax(data, "income");
			var yExtent = getMinMax(data, "lifeExpectancy");
			var rExtent = getMinMax(data, "population");
			var colorDomain = d3.nest().key(function(d) { return d.region }).object(newData);
			console.log("xExtent = ", xExtent, "yExtent = ", yExtent, "rExtent = ", rExtent);

// scales
			var xScale = d3.scaleLog()
				.domain([100, xExtent[1]])
				.range([0, width + margin.left]);
			var yScale = d3.scaleLinear()
				.domain([0, (yExtent[1] + 5)])
				.range([height, 0]);
			var rScale = d3.scaleSqrt()
				.domain(rExtent)
				.range([0,90]);
			var colorScale = d3.scaleOrdinal()
				.domain(colorDomain)
				.range(["Pink", "LightCyan", "Gainsboro", "Thistle", "MintCream", "LemonChiffon"]);

scales = {
				xExt : xExtent,
				yExt : yExtent,
				rExt : rExtent,
				color: colorDomain,
				xSca : xScale,
				ySca : yScale,
				rSca : rScale,
				cSca : colorScale
			};

// axes
			var x = d3.axisBottom()
				.scale(xScale)
				.ticks(10, ".0f");
			var y = d3.axisLeft()
				.scale(yScale);

// graph
      
      // Use nesting to set up the text labels
      data = d3.nest()
      	.key(function(d) {
        	return d.name
      })
      .entries(data);
      	
	
			// svg
			var svg = d3.select("body")
				.append("svg")
				.attr("width", width + margin.left + margin.right)
				.attr("height", height + margin.top + margin.bottom)
				.append("g")
				.attr("transform", "translate(" + margin.left + ", " + margin.top + ")");

// axes
			var xAxis = svg.append("g")
				.call(x)
				.attr("transform", "translate(0, " + height + ")");
			var yAxis = svg.append("g")
				.call(y);

// labels
			var xLabel = xAxis.append("text")
				.text("income per capita, inflation adjusted (dollars)")
				.attr("class", "axis")
				.attr("transform", "translate(" + (width + margin.left) + ", " + 0.5 * -margin.bottom + ")")
				.attr("text-anchor", "end");
			var yLabel = yAxis.append("text")
				.text("life expectancy (years)")
				.attr("class", "axis")
				.attr("transform", "translate(" + (margin.left * 0.85) + ", 0) rotate(-90)");
			var yrLabel = svg.append("text")
				.text(year)
				.attr("class", "year")
				.attr("transform", "translate(" + (width - 215) + ", " + (height - margin.bottom * 2.5) + ")")

// update(data, svg, scales, year);
			window.svg = svg;
			var interval = window.setInterval(function() {
				if (year > 2009) {
					year = 1950;
				}
				update(data, svg, scales, year);
				year++;
			}, 250);
		});
	</script>
</body>
</html>

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