title: Check if an array contains (only) numeric values
body: <p>I have arrays such as</p>
  
  <pre><code>var arrayVal_Int = ["21", "53", "92", "79"];   
  var arrayVal_Alpha = ["John", "Christine", "Lucy"];  
  var arrayVal_AlphaNumeric = ["CT504", "AP308", "NK675"];
  </code></pre>
  
  <ul>
  <li>Above <code>arrayVal_Int</code> should be considered as (purely) numeric.</li>
  <li><code>arrayVal_Alpha</code> and <code>arrayVal_AlphaNumeric</code> should be considered as strings.</li>
  </ul>
  
  <p>I need to check that in JavaScript.</p>