title: ready() working, on('ready') not working, why?
body: <p>I tried to use 'on' in my code but failed. The code I tried was this:</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-html lang-html prettyprint-override"><code>&lt;html&gt;
  
  &lt;head&gt;
    &lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"&gt;&lt;/script&gt;
    &lt;script type="text/javascript"&gt;
      function clickHandler(e) {
        alert('Click!');
      }
      $(document).on('ready', function() {
        $('#click_me').on('click', clickHandler);
      })
    &lt;/script&gt;
  &lt;/head&gt;
  
  &lt;body&gt;
    &lt;input id="click_me" type="button" value="click me" /&gt;
  &lt;/body&gt;
  
  &lt;/html&gt;</code></pre>
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  </div>
  </p>
  
  <p>Though I can replace this code with the code below. I still wonder why my first code with the event <code>on</code> didn't work.</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-html lang-html prettyprint-override"><code>&lt;html&gt;
  
  &lt;head&gt;
    &lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"&gt;&lt;/script&gt;
    &lt;script type="text/javascript"&gt;
      function clickHandler(e) {
        alert('Click!');
      }
      $(document).ready(function() {
        $('#click_me').click(clickHandler);
      })
    &lt;/script&gt;
  &lt;/head&gt;
  
  &lt;body&gt;
    &lt;input id="click_me" type="button" value="click me" /&gt;
  &lt;/body&gt;
  
  &lt;/html&gt;</code></pre>
  </div>
  </div>
  </p>