title: does the delete operator always return true if the object is defined?
body: <p>I have this:</p>
  
  <pre><code>console.log(
     delete ({a: true}['a'])
  );
  </code></pre>
  
  <p>that will log <code>true</code>.
  But so will this:</p>
  
  <pre><code> console.log(
      delete ({a: true}['b'])
   );
  </code></pre>
  
  <p>I am just trying to use a one-liner to return whether a key was present in the object before it was deleted.</p>
  
  <p>It looks like I have to do this instead?</p>
  
  <pre><code>  const v = {a: true};
    console.log(('b' in v) &amp;&amp; delete v['b']);
  </code></pre>
  
  <p>why doesn't the <code>delete</code> operator return false if <code>'b'</code> is not present in the object?</p>