title: Regular Expression Repeating Pattern separated by comma
body: <p>I have a regular expression of the following:</p>
  
  <pre><code>.regex(/^(?!^[0-9]*$)(?!^[a-zA-Z]*$)^([a-zA-Z0-9]{4})$/)
  </code></pre>
  
  <p>Must be exactly 4 characters
  Must contain at least 1 numeric and 1 alpha</p>
  
  <p>Although I rarely do regular expression, this was relatively easy.  I now have a new requirement that I have tried to implement, but cannot get right.</p>
  
  <p>New requirement:  Be able to have a comma separated list of the same type of input as before.  Cannot end with a comma.  Each item must be valid per the rules above (4 characters, at least on numeric, at least one alpha)</p>
  
  <pre><code>Valid:  123F,U6Y7,OOO8
  Invalid:  Q2R4,
  Invalid:  Q2R4,1234
  Invalid:  Q2R4,ABCD
  Invalid:  Q2R4,N6
  </code></pre>
  
  <p>I very much appreciate your help!
  Thanks!</p>