title: How to push into an array of object using the spread operator to a specific element
body: <p>I have an array  as such</p>
  
  <pre><code>const arr = [a={} , b={}]
  </code></pre>
  
  <p>Now I know the spread operator is not for mutation or pushing but it is very easy to do so with.</p>
  
  <p>I want this button to add elements to <code>a</code> when it's pressed </p>
  
  <pre><code> &lt;Button
  title= {this.props.title}
   onPress={ this.roomNumberPressed }
   /&gt;
  </code></pre>
  
  <p>so the end results be something like :</p>
  
  <pre><code>arr = [a={1,2,3} , b={3,4,5}]
  </code></pre>