title: Arrow function without curly braces
body: <p>I'm new to both ES6 and React and I keep seeing arrow functions. Why is it that some arrow functions use curly braces after the fat arrow and some use parentheses?
  For example:</p>
  
  <pre><code>const foo = (params) =&gt; (
      &lt;span&gt;
          &lt;p&gt;Content&lt;/p&gt;
      &lt;/span&gt;
  );
  </code></pre>
  
  <p>vs.</p>
  
  <pre><code>const handleBar = (e) =&gt; {
      e.preventDefault();
      dispatch('logout');
  };
  </code></pre>