title: assign a new property (a) to json object and give it a value of another property (b), then I want to change the (b) and keep (a) does not work
body: <pre><code>const obj = {
   a: 1,
   b:2,
   c:3
  } 
  const first = obj.a;
  obj.z = first;
  obj.a = '';
  
  </code></pre>
  <p>when I apply obj.a = ''; I get the result</p>
  <pre><code>const obj = {
   a: '',
   b:2,
   c:3,
   z:'',
  }
  
  </code></pre>
  <p>it causes obj.z to change too but I need to keep the original value of z --&gt; 1;</p>