title: Uncaught TypeError: d3.csv(...).then is not a function
body: <pre><code>    var allData;
      d3.csv('hello.csv', function(d) {
        return {
          id: +d.id,
          state: d.state
        };
      }).then(function(data) {
        allData = data;
      });
  </code></pre>
  
  <p>Above code is causing an error</p>
  
  <blockquote>
    <p>Uncaught TypeError: d3.csv(...).then is not a function</p>
  </blockquote>
  
  <p>I don't know what is wrong.</p>