title: javascript extract certain properties from all objects in array
body: <p>I have an array of objects with the same properties. Each object has around a hundred properties. I want to keep only a handful of them in a new array:</p>
  
  <pre><code>var dummyArray = [{ "att1": "something", "att2": "something", ..., "att100": "something"}, { "att1": "something", "att2": "something", ..., "att100": "something"}, ...];
  </code></pre>
  
  <p>How can I filter/map/reduce... and extract the interesting keys?</p>
  
  <pre><code>const newDummArray = dummyArray.map(function(item) { 
      delete item.att1; 
      delete item.att3; 
      delete item.att15;
      // ... (long list)
      return item; 
  });
  </code></pre>
  
  <p>how can I keep only <code>att20</code>, <code>att30</code>, <code>att70</code>, <code>att80</code> for each object and delete the rest?</p>