title: Why can't show the keyCode in console.log?
body: <p>I want to show all keyCodes when you type some characters in the input tag.
  ob is the input ,bind a function <code>checkWord</code> with event <code>onkeydown</code>, why <code>console.log</code> can't show its keycode value?</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>ob = window.document.getElementById("check");
  function checkWord(){
      console.log(onkeydown.keyCode);
  }
  ob.addEventListener("onkeydown",checkWord);  </code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code> 
  &lt;input id="check" type="text"&gt;
   </code></pre>
  </div>
  </div>
  </p>
  <p>I want <code>console.log</code> to show <code>65</code>  when I type <code>a</code> in the input tag.</p>