D3.js v4 Ladder Graph

This is a ladder graph created in D3.js v4 that:

is responsive,
is reusable,
and can have two different left-axes which can be switched between.

The data shows the fuel consumption and CO₂ emissions of cars, matched up with the "Eco rating" given when they were reviewed in the Guardian's 'On The Road' column, between July 2015 and July 2017.

You can view the data in a Google Sheet. Only conventional-fuel and hybrid cars are included.

Read more about the graph in my blog post.

For the difference between a slopegraph and a ladder graph, see Charlie Park's blog post.

View this as a gist or on bl.ocks.org.

<!DOCTYPE html>
<html lang="en-gb">
<head>
  <meta charset="UTF-8">
  <title>Ladder graph of cars' Eco Ratings</title>
  <link rel="stylesheet" href="style.css" />
</head>
<body>

<h1 class="chart-title">
    Cars reviewed in the Guardian’s <a href="https://www.theguardian.com/technology/series/ontheroad">‘On&nbsp;The&nbsp;Road’</a>&nbsp;column
  </h1>

(function() {

d3.json('data.json', function(error, data) {
        if (error) {
          throw error;
        };

var laddergraph = charts.laddergraph()
                          .leftKey1('Combined fuel consumption (mpg)')
                          .leftKey2('CO₂ emissions (g/km)')
                          .leftKey2Orientation('inverted')
                          .rightKey('Eco rating')
                          .tooltipFormat(function(d) {
                            var text = '<strong>' + d.Manufacturer + ' ' + d.Name + '</strong>';
                            text += '<dl>';
                            text += '<dt>Date reviewed</dt><dd>' + d.Date + '</dd>';
                            text += '<dt>Combined fuel consumption</dt><dd>' + d['Combined fuel consumption (mpg)'] + 'mpg</dd>';
                            text += '<dt>CO₂ emissions</dt><dd>' + d['CO₂ emissions (g/km)'] + 'g/km</dd>';
                            text += '<dt>Eco rating</dt><dd>' + d['Eco rating'] + '/10</dd>';
                            text += '</dl>';
                            return text;
                          });

d3.select('.js-laddergraph')
            .datum(data)
            .call(laddergraph);
      });

})();

</script>

</body>
</html>

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