Multiple line graph in v4 from JSON and draw()

This is a simple graph demonstrating the display of multiple lines. This was written using d3.js v4 and is a follow on to the simple graph example here.

This graph is part of the code samples for the update to the book D3 Tips and Tricks to version 4 of d3.js.

forked from d3noob's block: Multiple line graph in v4

forked from basilesimon's block: Multiple line graph in v4 from JSON and draw()

<!DOCTYPE html>
<meta charset="utf-8">
<style> /* set the CSS */

.line {
  fill: none;
  stroke: steelblue;
  stroke-width: 2px;
}
</style>
<body>

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

// set the dimensions and margins of the graph
var margin = {top: 20, right: 20, bottom: 30, left: 50},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

// parse the date / time
var parseTime = d3.timeParse("%Y");

// set the ranges
var x = d3.scaleTime().range([0, width]);
var y = d3.scaleLinear().range([height, 0]);

// define the line
var valueline = d3.line()
    .x(function(d) { return x(d.Date); })
    .y(function(d) { return y(d.Imports); });
// define the line
var valueline2 = d3.line()
    .x(function(d) { return x(d.Date); })
    .y(function(d) { return y(d.Exports); });
  
// append the svg obgect to the body of the page
// appends a 'group' element to 'svg'
// moves the 'group' element to the top left margin
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 + ")");

// Add the Y Axis
  svg.append("g")
      .call(d3.axisLeft(y));
  }
// Get the data
d3.json("data.json", function(error, data) {
  if (error) throw error;
  
  // trigger render
  draw(data, "Afghanistan");
});

</script>
</body>

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