title: How to know when finished
body: <p>Im pretty new to node.js, so i'm wondering how to know when all elements are processed in lets say:</p>
  
  <pre><code>["one", "two", "three"].forEach(function(item){
      processItem(item, function(result){
          console.log(result);
      });
  });
  </code></pre>
  
  <p>...now if i want to do something that can only be done when all items are processed, how would i do that?</p>