title: How to duplicate object properties in another object?
body: <p>Given the object:</p>
  
  <pre><code>var firstObject = {
      key1 : 'value1',
      key2 : 'value2'
  };
  </code></pre>
  
  <p><strong>how can I copy the properties inside another object</strong> (<code>secondObject</code>) like this:</p>
  
  <pre><code>var secondObject = {
      key1 : 'value1',
      key2 : 'value2',
      key3 : 'value3',
      key4 : 'value4'
  };
  </code></pre>
  
  <p>using a reference to the <code>firstObject</code>? Something like this:</p>
  
  <pre><code>var secondObject = {
      firstObject,
      key3 : 'value3',
      key4 : 'value4'
  };
  </code></pre>
  
  <p>(this doesn't work... I put it just to show in big lines how I would like to structure the code).</p>
  
  <p>Is a solution possible <strong>without</strong> using any JavaScript frameworks?</p>