title: Checking for a numerical index in a javascript array
body: <p>I'm receiving json data that is aggregated by numerical indexes.</p>
  
  <p>When I'm in my forloop, for example, the index might start at 1, which means in my forloop an error would occur because 0 doesnt exist.</p>
  
  <p>How do I check if a numerical index exists in the javascript array?</p>