title: How to do promise.all for array of array of promises?
body: <p>I am trying to run array of functions parallel and when everybody finishes I want work on that result.
  I am using promises. Now, I can put all functions in an array and can do 
  Promise.all(array of functions)
  But I have array like </p>
  
  <pre><code>[[promise1, promise2], [promise3,promise4], [promise5,promise6]],
  </code></pre>
  
  <p>where each promise is promisified function.
  Promise reference document says parameter in Promise.all should be an iterable object and my array is iterable.
  But it is not working for me. I think It is executing [promise1, promise2] as a promise but not individual promise.</p>
  
  <p>Can anybody please help me how I can achieve it or is there any better way ?</p>