title: How to find all combinations of items of multiple arrays
body: <p>Lets say these are the start arrays:</p>
  
  <pre><code>[a,b,c]
  [d]
  [e,f]
  </code></pre>
  
  <p>What algorithm could produce the following arrays?</p>
  
  <pre><code>[a,d,e]
  [a,d,f]
  [b,d,e]
  [b,d,f]
  [c,d,e]
  [c,d,f]
  </code></pre>
  
  <p>The number of start arrays can vary.</p>