title: Mixed JavaScript Array
body: <p>In the console I have an array that looks like this:</p>
  
  <pre><code>Array[3]
    0: Object
    1: Object
    2: Object
    columns: Array[2]
    length: 3
    __proto__: Array[0]
  </code></pre>
  
  <p>The last item hasn't an index, but the name <code>columns</code>.</p>
  
  <p>How can I reproduce something similar?
  I tried:</p>
  
  <pre><code>var columns = ["age", "population"];
  var myObj = [
    {age: "&lt;5",     population: 2704659},
    {age: "5-13",  population: 4499890},
    {age: "14-17", population: 2159981},
    columns
  ];
  console.log(myObj);
  </code></pre>
  
  <p>But it gives me this:</p>
  
  <pre><code>// Console
  Array[4]
    0: Object
    1: Object
    2: Object
    3: Array[2]
    length: 4
    __proto__: Array[0]
  </code></pre>