Nations Line Graph v2

<!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; }
    
    .labels {
      font-family: "Calibri";
      font-size:26px;
      stroke: gray
    }
    
    .axes{
   		fill: black
    }
    
    path{
      stroke: #c7cdd6;
      stroke-width: 2;
      fill: none;
    }
    
    #lineStyle {
      fill: none;
      stroke: #5ec997;
      stroke-width: 3
    }
    
  	#countrySelect{
      position:absolute;
      top:10px;
      left:100px;
		}
  </style>
</head>

<body>
  <script>
 
var margin = {top: 20, right: 40, bottom: 20, left: 40};
var width = 960 - margin.left - margin.right
var height = 500 - margin.top- margin.bottom

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 + ")");

//reading the data file & setting callback function
	var data = d3.json("nations.json", main)

var yScale = d3.scaleLinear()
        .domain([20, maxLifeExpectancy])
        .range([height, 0]);
 
  //set axis & call axis
    var xAxis = d3.axisBottom()
        .scale(xScale)
    		.tickFormat(d3.format("d"))

var yAxis = d3.axisLeft()
      	.scale(yScale)
    
    svg.selectAll("*").remove();
  
    svg.append("g")
    	.attr("transform", "translate (" + 0 + "," + height +")")
    	.attr("class", "axes")
      .call(xAxis);

svg.append("g")
      .attr("class", "axes")
      .call(yAxis);
    
    svg.append("text")
    	.attr("class", "labels")
    	.attr("transform", "translate(" + (width - 50) + "," + (height - 20) + ")")
    	.text("Year")

svg.append("text")
    	.attr("class", "labels")
    	.attr("transform", "rotate(-90)")
      .attr("y", margin.left)
      .attr("x",0 - (height - 300))
    	.text("Life Expectancy")
      
    svg.append("path")
    	.attr("id", "lineStyle")
      .datum(selection.lifeExpectancy)
      .attr("d", line);
  }
  };

</script>
</body>

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