title: In Lodash.js/Underscore.js, how to add index for every element?
body: <p>Here is the input:</p>
  
  <pre><code>[{animal: "cat"}, {animal:"dog}}
  </code></pre>
  
  <p>And the output would be :</p>
  
  <pre><code>[{animal: "cat", idx: 1}, {animal: "dog", idx: 2}]
  </code></pre>
  
  <p>Does anyone have ideas about how to do this in Lodash/Underscore.js?</p>