title: Check variables and add them to comma separated list
body: <p>I have 4 javascript variables:</p>
  <pre><code>a = 'first';
  b = 'second';
  c = 'third';
  d = 'fourth';
  </code></pre>
  <p>What i want to achieve is to get them separated by comma, BUT. Sometimes where could be situations that some variables could be empty. Here is some of examples:</p>
  <p>EXAMPLE1:</p>
  <pre><code>a = 'first';
  b = '';
  c = 'third';
  d = '';
  </code></pre>
  <p>OUTPUT should be: first, third</p>
  <p>EXAMPLE2:</p>
  <pre><code>a = '';
  b = 'second';
  c = '';
  d = 'fourth';
  </code></pre>
  <p>OUTPUT should be: second, fourth</p>
  <p>Maybe someone could help me to solve this?</p>