old_contents: import React, { PropTypes } from 'react';
  
  const Link = ({ active, children, onClick }) => {
    if (active) {
      return <span>{children}</span>;
    }
  
    return (
      <a
        href="#"
        onClick={e => {
          e.preventDefault();
          onClick();
        }}
      >
        {children}
      </a>
    );
  };
  
  Link.propTypes = {
    active: PropTypes.bool.isRequired,
    children: PropTypes.node.isRequired,
    onClick: PropTypes.func.isRequired,
  };
  
  export default Link;
  
new_contents: import React, { PropTypes } from 'react';
  
  const Link = ({ active, children, onClick }) => {
    if (active) {
      return (
        <span className="link">
          {children}
        </span>
      );
    }
  
    return (
      <a
        className="link"
        href="#"
        onClick={e => {
          e.preventDefault();
          onClick();
        }}
      >
        {children}
      </a>
    );
  };
  
  Link.propTypes = {
    active: PropTypes.bool.isRequired,
    children: PropTypes.node.isRequired,
    onClick: PropTypes.func.isRequired,
  };
  
  export default Link;
  
subject: Add special class to every Link element