MY first version of function.html

<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <title></title>
  </head>
  <body>
    <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>
      <script>
        function oneplusone(){
        document.write(1+1+'<br>');
      }
        oneplusone();
        function sum(left,right){
          document.write(left+right+'<br>');
        }
        sum(2,3); //5
        sum(3,4); //7 this code has some problem
      </script>
      <h2>return</h2>
      <script>
        function sum2(left,right){
          return left+right;
        }
        document.write(sum2(2,3)+'<br>');
        document.write('<div style="color:red">'+sum2(2,3)+'</div>');
        document.write('<div style="font-size:100px">'+sum2(2,3)+'</div>');
      </script>
  </body>
</html>