title: After using babel to compile, why does const、let、arrow function still exist？
body: <p><a href="https://i.stack.imgur.com/VKWt1.png" rel="nofollow noreferrer">using babel to compile</a></p>
  <p>before</p>
  <pre class="lang-js prettyprint-override"><code>let name=&quot;Alex&quot;;
  const age=18;
  const add=(x,y)=&gt;x+y;
  
  </code></pre>
  <p>after using babel to compile</p>
  <pre class="lang-js prettyprint-override"><code>&quot;use strict&quot;;
  let name = &quot;Alex&quot;;
  const age = 18;
  const add = (x, y) =&gt; x + y;
  </code></pre>
  <p>I'm just really confused, why it didn't change anything at all.</p>