title: Why use element[0] instead of element when creating AngularJS directive with d3?
body: <p>It seems that you have to use <code>element[0]</code> when creating a directive with D3, for example, like below:</p>
  
  <pre><code>app.directive('firstTry', function () {
      function link(scope, element, attrs) {
          var sampleSVG = d3.select(element[0])
          ...
  </code></pre>
  
  <p>So, why <code>element[0]</code> but not <code>element</code>? The name <code>element</code> suggests that it is a single object rather than an array, but apparently that's not the case. Another question: what else does this <code>element</code> have? </p>
  
  <p>BTW, any official references about this matter would greatly help.</p>
  
  <p>Thank you very much.</p>