title: Correct way to permanently alter a JavaScript string
body: <p>In Ruby, if I want to modify a string and have it change the original string, I can use the <code>!</code> bang character. </p>
  
  <pre><code>string = "hello"
  string.capitalize!
  &gt; "Hello"
  string
  &gt; "Hello" 
  </code></pre>
  
  <p>In JavaScript, I can't find this equivalence. Modifying a string to be <code>upperCase</code> for instance returns the original string after the first instance.</p>
  
  <pre><code>var string = "hello";
  string.toUpperCase();
  &gt; "HELLO"
  string
  &gt; "hello"
  </code></pre>
  
  <p>I know I can save it as a variable such as </p>
  
  <pre><code>var upperCaseString = string.toUpperCase();
  </code></pre>
  
  <p>but this seems inefficient and is undesirable for my purposes.  </p>
  
  <p>I know it must be obvious, but what am I missing?</p>