<h1>Function</h1>
    <h2>Basic</h2>
    <ul>
      <script>
        function two(){
          document.write('<li>2-1</li>');
          document.write('<li>2-2</li>');
        }
        document.write('<li>1</li>');
        two();
        document.write('<li>3</li>');
        two();
      </script>
    </ul>
    <h2>Parameter & Argument</h2>
    <h2>Return</h2>

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