title: Object spread with common keys
body: <p>Consider this:</p>
  <pre><code>let obj1 = {id: 1, common_key: &quot;one&quot;, property1: &quot;property_one&quot;}
  let obj2 = {id: 1, common_key: &quot;two&quot;, property2: &quot;property_two'&quot;}
  
  let merged = {...obj1, ...obj2}
  console.log(merged)
  </code></pre>
  <p>Output:</p>
  <pre><code>{id: 1, common_key: &quot;two&quot;, property1: &quot;property_one&quot;, property2: &quot;property_two'&quot;}
  </code></pre>
  <p>We see that <code>common_key</code> from <code>obj2</code> is taken over (value - <code>&quot;two&quot;</code>) in this merge.<br />
  Does this mean where when there is a collision of common key in an object spread (merge) it is guaranteed that the one that come later wins? If yes, is this mentioned somewhere in ES6 spec?</p>