title: React Updating Arrays in State
body: <p>I am using react-native-maps and trying to draw multiple polylines. I have grouped points in this structure in state:</p>
  
  <pre><code>var groups = [{
      Key: 'YELLOW',
      Points: [],
  }]
  </code></pre>
  
  <p>Now I want to push lat/lng objects in Points array but it gives object not extensible error. I tried to expand attibutes using [... this.state.groups] but I can't push Points in it.</p>
  
  <p>I have a separate array which contains a similar structure which has all the points data. The concept here is that I need to push that data in to this group data structure with a delay for each point so the polylines/route draws slowly.</p>