Multi-Series Lince Chart D3 demo

from: http://bl.ocks.org/mbostock/3884955

HTML

<script src="http://d3js.org/d3.v3.js"></script>
<!DOCTYPE html>
<!-- 
Multi-Series Line Chart D3 demo from:
http://bl.ocks.org/mbostock/3884955

Instuctions:
* download http://f.dtkav.com/data.tsv
* click [choose file]/[browse] in the run pane
* chose data.tsv
-->

<body>
    <div>
        <input id="uploader" type="file" />
    </div>
</body>

CSS

body {
  font: 10px sans-serif;
}

.axis path,
.axis line {
  fill: none;
  stroke: #000;
  shape-rendering: crispEdges;
}

.x.axis path {
  display: none;
}

.line {
  fill: none;
  stroke: steelblue;
  stroke-width: 1.5px;
}

JavaScript

var reader = new FileReader();
  
reader.onload = function(e) {
  var contents = e.target.result;
  var data = d3.tsv.parse(contents)
  d3plot(data);
};

var uploader = document.getElementById("uploader");  
uploader.addEventListener("change", handleFiles, false);  

function handleFiles() {
  var file = this.files[0];
  reader.readAsText(file);
};

function textarea(data) {
  document.getElementById("csv").value = JSON.stringify(data);
}


var margin = {top: 20, right: 80, bottom: 30, left: 50},
    width = 960 - margin.left - margin.right,
    height = 500 - margin.top - margin.bottom;

var parseDate = d3.time.format("%Y%m%d").parse;

var x = d3.time.scale()
    .range([0, width]);

var y = d3.scale.linear()
    .range([height, 0]);

var color = d3.scale.category10();

var xAxis = d3.svg.axis()
    .scale(x)
    .orient("bottom");

var yAxis = d3.svg.axis()
    .scale(y)
    .orient("left");

var line = d3.svg.line()
    .interpolate("basis")
    .x(function(d) { return x(d.date); })
    .y(function(d) { return y(d.temperature); });

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 + ")");

function d3plot(data) {
  color.domain(d3.keys(data[0]).filter(function(key) { return key !== "date"; }));

  data.forEach(function(d) {
    d.date = parseDate(d.date);
  });

  var cities = color.domain().map(function(name) {
    return {
      name: name,
      values: data.map(function(d) {
        return {date: d.date, temperature: +d[name]};
      })
    };
  });

  x.domain(d3.extent(data, function(d) { return d.date; }));

  y.domain([
    d3.min(cities, function(c) { return d3.min(c.values, function(v) { return v.temperature; }); }),
    d3.max(cities, function(c) { return d3.max(c.values, function(v) { return v.temperature; }); })
  ]);

  svg.append("g")
      .attr("class", "x...