Why doesn't my arrow function return a value? : <p>I have an arrow function that looks like this (simplified):</p>

<pre><code>const f = arg =&gt; { arg.toUpperCase(); };
</code></pre>

<p>But when I call it, I get <code>undefined</code>:</p>

<pre><code>console.log(f("testing")); // undefined
</code></pre>

<p>Why?</p>

<p>Example:</p>

<p><div class="snippet" data-lang="js" data-hide="true" data-console="true" data-babel="false">
<div class="snippet-code snippet-currently-hidden">
<pre class="snippet-code-js lang-js prettyprint-override"><code>const f = arg =&gt; { arg.toUpperCase(); };
console.log(f("testing"));</code></pre>
</div>
</div>
</p>

<hr>

<p><em>(<strong>Note:</strong> This is meant to be a clean, canonical dupetarget for the <strong>specific</strong> issue with arrow functions above.)</em></p>
