Fake Genes and animation with numbers

<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  </style>
</head>

<body>
  <script>
    
    var svg = d3.select("body").append("svg")
      .attr("width", 960)
      .attr("height", 500)
    var genemap= [{"name": "1", "start": 50, "end": 100, "direction":"F", "function": "function 1", },{"name": "2", "start": 180, "end": 300, "direction":"F", "function": "function 2", },{"name": "3", "start": 260, "end": 400, "direction":"R", "function": "function 3", },{"name": "4", "start": 380, "end": 600, "direction":"F", "function": "function 4", },]
    
svg.selectAll("rect")
    	.data(genemap)
    	.enter()
    	.append("rect")
    	.attr("x", function(d) {if (d.direction=="F") {return 0-(d.end-d.start);} else{return 1000;}})
			.attr("width", function(d) {return d.end - d.start;})
			.attr("y", function(d) {if (d.direction =="F") {return 100;} else{return 200;}})
    	.attr("height", 50)
    	.attr("fill", function(d) {if (d.direction=="F") {return "cyan";} else{return "pink";}})
    	.attr("stroke", "black")
			.transition()
			.duration(2000)
			.delay (function (d, i) {return i *1000})
			.attr("x", function(d) {return d.start;})
svg.selectAll("text")
	.data(genemap)
	.enter()
	.append("text")
	.text(function(d) {return d.name})
	.attr("font-size", 20)
	.attr("font-family", "Times New Roman")
	.attr("x", function(d) {if (d.direction=="F") {return 0-(d.end-d.start);} else{return 1000;}})
	.attr("y", function(d) {if (d.direction =="F") {return 130;} else{return 230;}})
  .transition()
			.duration(2000)
			.delay (function (d, i) {return i *1000})
			.attr("x", function(d) {return d.start;})

//.attr("fill", function(d) {if (d.direction=="F", d.name=="1") {return "green";} else if(d.name=="2") {return "yellow";} else if(d.name=="4") {return "purple";} else {return "blue"}})
    
  </script>
</body>

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