title: Add new key:value pairs to existing an existing array
body: <p>Here's my existing data:</p>
  
  <pre><code>var nodes = [
      {i: 0, radius: 18.637872483796723},
      {i: 0, radius: 17.174333481950903},
      {i: 0, radius: 13.194447610161163},
      {i: 1, radius: 8.000718059188364},
      {i: 1, radius: 4.08204211857112}
    ];
  </code></pre>
  
  <p>I need to add one new key:value pairs for each item in the list. It is dynamically calculated: </p>
  
  <pre><code>cx: i*2
  </code></pre>
  
  <p>So the new array would look like this:</p>
  
  <pre><code>[
    {i: 0, radius: 18.637872483796723, cx: 0},
    {i: 0, radius: 17.174333481950903, cx: 0},
    {i: 0, radius: 13.194447610161163, cx: 0},
    {i: 1, radius: 8.000718059188364, cx: 2},
    {i: 1, radius: 4.08204211857112, cx: 2}
  ];
  </code></pre>
  
  <p>I am a beginner, so excuse any terminology that I've butchered (I'm not sure if I'm using the term array correctly).</p>