title: How to get sum of an array object keys in underscore.js?
body: <p>I have the following array:</p>
  
  <pre><code>var items = [
     {price1: 100, price2: 200, price3: 150},
     {price1: 10, price2: 50},
     {price1: 20, price2: 20, price3: 13},
  ]
  </code></pre>
  
  <p>I need to get object with sum of all keys like the following:</p>
  
  <pre><code>var result = {price1: 130, price2: 270, price3: 163};
  </code></pre>
  
  <p>I know I may to use just loop but I'm looking for a approach in underscore style :)</p>