gistfile1.txt

var footer = data.source || data.tools ? (
  <p>
    {data.source ? () : null}
    {data.tools ? data.tools.join(', ') : null}
  </p>
) : null;

...

return (
  <div className="project-footer">
    <p className="project-description">{data.desc}</p>
    {footer}
  </div>
);